Chapter Summaries

Dumbledore and Snape took Harry and Yinsen into the Chamber of Secrets and defeated the Basilisk while Harry only opened the entrance. Dumbledore questioned Yinsen afterward, concluded he was not an enemy, and let him continue at Hogwarts; Yinsen returned to the Chamber to claim the Basilisk’s meat.

• McGonagall objected to bringing Harry and Yinsen into the Chamber, but Dumbledore insisted and told Snape to protect them.
• Snape, Dumbledore, Harry, and Yinsen entered the Chamber, where the professors drew out and defeated the Basilisk while Harry and Yinsen watched.
• Dumbledore kept Yinsen behind for a private conversation and asked whether Yinsen Arendelle was his true name and whether he knew Tom Riddle was Voldemort.
• Yinsen openly dismissed Voldemort, and Dumbledore decided after testing him that he was not their enemy and could remain at Hogwarts.
• After Dumbledore let him leave, Yinsen returned to the Chamber of Secrets to get the Basilisk’s meat.

Yinsen destroyed the Basilisk and the soul fragment in Tom Riddle’s diary, then rescued Ginny and stored the creature’s body. Hogwarts returned to a peaceful routine, while Yinsen continued studying advanced magic from Snape’s private collection and Snape grew increasingly aware of his power.

• Yinsen disintegrated Tom Riddle’s memory and soul fragment, causing the diary to burn as Ginny lay unconscious.
• Yinsen stored the Basilisk’s corpse when Ginny woke, then explained what had happened and led her out of the Chamber of Secrets.
• Ginny thanked Yinsen and hurried back to Gryffindor, while Scáthach revealed she had wanted the Basilisk for crafting materials.
• Hogwarts settled into peaceful days, with Hermione studying under Rin Tohsaka and Yinsen pursuing his studies.
• Yinsen browsed Snape’s private spellbooks, and Snape recognized the strength behind Yinsen’s magic and suspected he was more than an ordinary teenager.

Snape grew suspicious of Yinsen and Scáthach but began discussing magic with Yinsen, whose explanations greatly improved Snape’s spellcasting. Yinsen arranged to borrow restricted books through Snape, then was caught by Illya after skipping classes all day.

• Snape suspected that Yinsen and the other children were not ordinary students, and he feared Scáthach might be the legendary figure of that name.
• Yinsen told Snape he had come to Hogwarts to learn, then impressed him with his deep understanding of spells and Potionology.
• Snape discussed magic with Yinsen for more than half a day and learned to cast Sectumsempra silently without a wand.
• Yinsen asked Snape to borrow as many books as possible that students could not access, and Snape agreed.
• After leaving Snape’s office, Yinsen was caught by Illya for skipping classes all day and dismissed Defense Against the Dark Arts as a waste of time.

Yinsen and his companions shared a stew made from the Basilisk with Harry, Ron, and Hermione, while his school life with Dumbledore and Snape remained peaceful. As summer vacation began, Yinsen planned to travel among several worlds before deciding where to spend the break.

• Yinsen used rare ingredients obtained through Snape to prepare a huge pot of Basilisk stew, and Harry, Ron, Hermione, and Rin Tohsaka joined the group for dinner.
• Yinsen told the guests that the delicious stew was snake meat from the Chamber of Secrets, and everyone continued eating until the pot was empty.
• After dinner, Hermione asked about Christmas plans and learned she was the only one among them who intended to go home.
• Yinsen left the Book of Inheritance with Snape, who recognized its name as Merlin's Legacy Tome and later asked Yinsen about Runes.
• When summer vacation arrived, Yinsen planned to return to the Moon Goddess, check on Soujun, and visit Arthur's World, the Starship Troopers world, and the Marvel Universe.

Yinsen sent O'Connell, Jonathan, and Maria Hill to the G.I. Joe world to retrieve nanotechnology and powered exoskeleton technology, while he upgraded the Teleportation Device and checked on Cherry Military Industries. He then visited Arthur's world, where Artoria was serving in the rebellion suppression campaign, and she greeted him with a happy smile.

• Yinsen offered O'Connell a mission to acquire technology from the G.I. Joe world, and Jonathan and Maria Hill joined his team.
• Yinsen and Luna upgraded the Teleportation Device and sent the team to the G.I. Joe world.
• Yinsen checked Cherry Military Industries' progress on the Greatsword Rifle and Iron Monger before returning to the Moon Goddess.
• Yinsen sent Rin Tohsaka and Illya to Arthur's location, where Arthur was judging captured traitors and Artoria was having dinner with Shirou Emiya.
• Artoria, whose doubts had eased after the campaign, smiled happily when Yinsen arrived with Rin Tohsaka.

Artoria resolved her inner conflict and chose to accept her ending, while Yinsen prepared for Harry Potter’s third year by studying time reversal and securing a creature from the Edge of Tomorrow world. Afterward, he invited Bruce Banner to travel with him to the Marvel Universe through the newly established passage.

• Artoria thanked Yinsen and decided to help Arthur quell the rebellion before returning to face her accepted ending.
• Shirou Emiya introduced Artoria to a game featuring a version of herself, and Illya gave her a phone.
• Yinsen checked on Soujun’s progress in the YuYu Hakusho world and sent Medea there to join him.
• Yinsen visited the Edge of Tomorrow world, tested the aliens’ time reversal, and stored the largest creature’s corpse for his research on the Time-Turner.
• Yinsen invited Bruce Banner to the Marvel Universe, and Banner agreed to go with him.

Yinsen traveled with Bruce Banner to the Marvel Universe to tell Tony Stark about the new connection and give him a Positioning Device, but Tony fled before they could talk properly. After Yinsen separated from Banner at Avengers headquarters, a young woman mistook him for a lost child.

• Illya stayed aboard the Moon Goddess to tutor Shirou Emiya and arranged for Scáthach to train him in combat.
• Bruce Banner told Yinsen that Little Ou had been burying magic stones at the foot of the mountain, and Yinsen decided to investigate later.
• Yinsen and Banner teleported to Yinsen's mansion, where J.A.R.V.I.S. recognized Yinsen despite his childlike appearance.
• Yinsen teleported to Avengers headquarters and met Tony, who photographed and filmed his new appearance before fleeing with Blink Magic.
• Yinsen separated from Banner to explore the headquarters, and a young woman in a Red Jacket asked whether he had been separated from his family.

Yinsen discovered that Tony had recruited Wanda and Pietro after rescuing them from Hydra experiments, making Wanda his magic disciple and Pietro a combat trainee. Tony introduced Yinsen as his own magic teacher, leaving Wanda and Pietro stunned.

• Yinsen suspected Tony had sought out Wanda and Pietro, then went with Wanda to the lounge where Pietro was waiting for Banner.
• Yinsen read the Avengers' internal files and learned that Tony had rescued the siblings from a Hydra laboratory after they volunteered for experiments.
• The files revealed that Wanda's mental power and Pietro's speed and agility had been enhanced, and that Tony had helped them find the person responsible for the attack on their home.
• Wanda became Tony's disciple to learn magic, while Pietro trained in combat with Steve Rogers and Clint Barton.
• Tony admitted that he was teaching Wanda to warp reality, and Yinsen warned that she could currently do little more than twist someone's neck.
• Tony introduced Yinsen to Wanda and Pietro as the mysterious Avenger who had taught him magic.

Yinsen visited the Avengers and explained that he had established a stable passage between the worlds, allowing Tony Stark and others to reach him more easily. After discussing travel options and Bruce Banner’s role with the Avengers, Yinsen reunited with Steve Rogers and reflected on the few major threats that remained.

• Yinsen explained to Wanda and Pietro that special circumstances had turned him into a child, then sent them off with Tony Stark.
• Yinsen gave Tony Stark information and data for building a Teleportation Device, and planned to add his world as a destination to Thor’s Stormbreaker.
• Tony Stark said the Avengers still needed Bruce Banner for his scientific abilities, and mentioned that Doctor Zhao was their medical consultant.
• Steve Rogers met child-bodied Yinsen, accepted his explanation, and learned that the Avengers could contact him through the stable passage.
• Yinsen considered that most threats from the original events had been avoided, but remembered Thanos and Dormammu as dangers still facing Earth.

Yinsen met with Odin on Earth to assess his failing body and soul, then agreed to preserve Odin’s soul core in a long sleep. The Ancient One offered Odin a reason to awaken again by exploring new worlds, and Odin accepted just before his body collapsed into a sphere of light.

• Yinsen visited Asgard, learned Odin was on Earth, and called him to arrange a meeting.
• Yinsen examined Odin and realized that his body and soul were worn down by a long life, not merely damaged or ill.
• Odin agreed to let Yinsen preserve his soul core so he could sleep and be awakened if needed.
• The Ancient One arrived and invited Odin to explore other worlds after he woke, and Odin accepted the invitation.
• Odin’s body collapsed into a sphere of light, leaving Yinsen unprepared as he began preserving him.

Yinsen contained Odin’s collapsing soul core in a layered Ice Coffin and returned to Kamar-Taj with the Ancient One, who praised his growing ability to borrow time’s power. They discussed Doctor Strange’s coming arrival and arranged an easier way for the Ancient One to visit Yinsen’s universe.

• Yinsen combined blue and green magic with layers of Ice Crystal to seal Odin’s soul core inside a reinforced Ice Coffin.
• Frigga took the Ice Coffin through a portal to Asgard, then Yinsen and the Ancient One returned to Kamar-Taj.
• The Ancient One recognized that Yinsen had used borrowed time power, and he explained how studying the Eye of Agamotto and using his Space-Time Pointer had helped him.
• Yinsen and the Ancient One discussed Doctor Strange’s future and her wish for Yinsen to help guide him.
• Yinsen told the Ancient One that he had connected his universe to hers and explained how she could travel there.

Yinsen returned from Kamar-Taj to Avengers Base, where Tony and the others discussed the Avengers’ work and Tony’s plans to build a Teleportation Device. He watched Wanda demonstrate her Reality Gem-based magic and recognized it as Chaos Magic.

• After confirming the Ancient One’s plan was proceeding as intended, Yinsen left Kamar-Taj and returned to Avengers Base.
• Yinsen joined Tony, Steve, and the other Avengers at an informal meeting, where Tony agreed to finish installing Doctor Zhao’s medical pod before working on a Teleportation Device.
• Tony told the Avengers that the device could let them travel between worlds and call on Yinsen for help during major trouble.
• Tony tossed Wanda an apple and asked her to demonstrate the magic she had been learning.
• Wanda permanently transformed the apple into iron, and Yinsen recognized her spell as Chaos Magic.

Yinsen checked in with Tony and the Avengers, then returned to the Moon Goddess and caught up with Diana, Sherry, and Laura. While exploring the island, he discovered that Little Ou had cultivated a Magic Stone mine and could eventually produce higher-grade stones.

• Tony explained that Wanda was learning both magic and scientific subjects, while Yinsen praised his teaching.
• Yinsen and Tony discussed preparing the Underground Laboratory equipment for The Ancient One and agreed to plan a future trip together.
• Yinsen returned to the Moon Goddess, reviewed the status of his other worlds, and spent time with Diana before bringing back Sherry and Laura.
• Laura learned Logan's appearance had changed and went to speak with her father, while Yinsen searched the island for Little Ou.
• Yinsen found a concealed cave near Little Ou and discovered a Magic Stone mine that Little Ou had grown; Little Ou claimed it could produce higher-grade stones over time.

Yinsen discovered that Magic Stones could nourish his body, so he helped Little Ou upgrade its mine and took a supply for himself. He then visited Arthur’s world, found everyone absorbed in a game, and offered to accompany Arthur on a future trip to another world.

• Yinsen realized his body absorbed Magic Stone energy directly, and Little Ou promised to produce higher-quality stones with a better energy supply.
• Yinsen expanded the mine’s energy channels and learned how Little Ou upgraded its Magic Stone-producing structure.
• Yinsen rewarded Little Ou with snacks, filled a bag with Magic Stones, and returned to Logan’s cabin.
• Yinsen found Laura and Logan finished talking, then wondered whether to revive Illya’s artificial Maids.
• Yinsen visited Arthur’s world, found the group playing games, and quietly went to speak with Arthur.
• Yinsen and Arthur discussed a future journey together after Arthur passed the throne to Mordred.

After returning from Arthur’s Britain, Yinsen and the others helped Artoria face her final moments and return to her own world. Yinsen intercepted Merlin’s attempt to take her away, healed her, and reunited her with Shirou Emiya, but Excalibur soon fell between them.

• Artoria returned with the group to the island and agreed to settle her final affairs in her own time.
• Yinsen showed Shirou Emiya and Cú Chulainn an image of Artoria’s last moments, as she instructed Bedivere to return Excalibur to the Lady of the Lake.
• As Merlin began to take Artoria away, Yinsen intervened and brought her back to the group.
• Yinsen healed Artoria’s wounds and replenished her life force, and she told Shirou Emiya, “I’m back, Shirou.”
• Excalibur fell from the sky and embedded itself between Artoria and Shirou Emiya.

Yinsen brought Artoria back to the Moon Goddess and began training Shirou Emiya, whose new magic made blindly copying Emiya’s techniques unsuitable. After a month of intensive practice, Yinsen decided Shirou needed real combat to discover his own path, and prepared to send him to face a Demon King alongside Sanada and his companions.

• Artoria realized that, now living in a human body, she could no longer make her armor and sword disappear like a Servant, though the Moon Goddess’s equipment could solve the problem.
• Yinsen returned with Artoria and Shirou Emiya to the Moon Goddess, where the others welcomed Artoria and Shirou agreed to train with Yinsen.
• Yinsen and Artoria put Shirou through intensive combat training, breaking his projected weapons as he gradually improved.
• Yinsen told Shirou that Emiya’s techniques were only references because Shirou’s different magic meant he needed to develop methods suited to himself.
• Yinsen explained that Shirou needed real combat and introduced his next assignment: helping Sanada and his companions fight a Demon King seeking control of the human world.

Yinsen returned to Hogwarts for the new school year and encountered Dementors on the train. When one threatened Leah and Harry, he used the Patronus Charm to conjure a dragon that destroyed and swallowed it, leaving Lupin stunned.

• Yinsen returned to Harry Potter World with the others and prepared for the new school year while planning to research a Time-Turner.
• Yinsen and his companions sensed Dementors near Hogwarts after the Ministry deployed them to search for Sirius Black.
• The train stopped, and Yinsen discovered that Rin Tohsaka and Leah had gone to find Hermione.
• Yinsen hurried to Harry's compartment when a Dementor approached Leah, then cast the Patronus Charm.
• Yinsen's dragon-shaped Patronus tore apart and swallowed the Dementor as Lupin and Hermione watched in shock.

Yinsen explained to Dumbledore, Snape, and Lupin that Sirius had not betrayed the Potters and that the real traitor was hiding at Hogwarts. The chapter ended with Yinsen hinting that Peter Pettigrew had survived despite being believed dead.

• Yinsen drove off the Dementor and introduced himself to Lupin before the train reached Hogwarts.
• After the feast, Dumbledore summoned Yinsen, Snape, and Lupin to discuss the Dementor attack and Harry Potter.
• Yinsen told Dumbledore that Sirius would not harm Harry and that someone else had betrayed the Potters.
• Yinsen revealed that the real traitor was currently hiding at Hogwarts, shocking Dumbledore, Snape, and Lupin.
• When Lupin noted that Peter Pettigrew was dead, Yinsen suggested that losing a finger did not prove Peter had died.

Yinsen revealed that Peter Pettigrew was hiding as Ron Weasley's pet rat, prompting Dumbledore to capture him and reconsider Sirius's case. After Snape asked whether Yinsen could cure Lupin's lycanthropy, Yinsen said he could.

• Yinsen identified Scabbers as Peter Pettigrew, and Dumbledore discussed the complications of clearing Sirius's name with Snape and Lupin.
• Dumbledore and his trusted helpers captured Peter Pettigrew, while Scáthach secretly watched.
• Dumbledore sought out Sirius, who had infiltrated Hogwarts, and kept him from meeting Harry Potter.
• Snape asked Yinsen whether he could solve Lupin's werewolf transformation problem.
• Yinsen answered that he could cure Lupin.

Yinsen removed the werewolf virus from Lupin, ending his involuntary transformations and curing the pain caused by the treatment. Lupin asked who Yinsen was, and Yinsen said he was a mage spending a few years at Hogwarts.

• Snape asked Yinsen to help Lupin, and Yinsen agreed to examine and treat him.
• Dumbledore brought Lupin and McGonagall to his office, where Yinsen explained that removing the virus would solve Lupin’s condition.
• Yinsen used wandless magic to draw the werewolf virus from Lupin, causing him severe pain and silencing his screams.
• Yinsen healed Lupin’s throat, burned away the extracted substance, and told him he could now look at the moon without transforming.
• Lupin asked Yinsen who he was, and Yinsen described himself as a mage visiting Hogwarts to learn and do good deeds.