An unnatural flush spread across the Slit-Mouthed Woman's face, and her gray eyes brimmed with mist.
It took a long while before she regained control of her body. Then she slowly rose from the couch, repeatedly clenching and unclenching her fists or touching the objects around her, exploring the world anew like a cursed spirit that had only just been born.
At last, she gradually grew accustomed to the new power inside her. She now had two cursed energy cores: one was Sukuna's Finger, and the other was her own core as the specific entity known as the "Special Grade Imaginary Cursed Spirit: Slit-Mouthed Woman." These two cores could connect with each other, producing an effect where 1 + 1 > 2.
If she had previously been a purely gas-powered car or a purely electric car, she had now become a range-extended vehicle. Even when the battery ran out, she could still burn fuel in the range extender to power the motor.
However, she had to make some changes when using her powers. At the very least, there was now an extra step in the process of "activating cursed energy." She first had to draw a trace of Sukuna's power from his finger and guide it into her own cursed energy core, then operate her core to activate her cursed energy normally. That way, both cores could start up at once, much like a range-extended vehicle's HEV mode.
Without that extra step, she would effectively not be using Sukuna's Finger at all, casting her cursed technique with her original cursed energy core instead. That was equivalent to a range-extended vehicle's EV mode.
Seeing that his Miss Slit-Mouthed Woman had more or less recovered, Shoichi Kano cautiously approached. "Are you... all right now?"
"Those noises Mommy was making just now..." The Slit-Mouthed Woman abruptly remembered how long she had been moaning like that. "Did you hear all of them?"
Kano spread his hands. "What do you think?"
To tease the cursed spirit, he even took out his phone and waved it at her. "I even recorded them."
With that, he pulled a few tissues from the box on the coffee table, turned around, and headed into the bathroom. "I'm going to enjoy them again."
Now the Slit-Mouthed Woman started to panic. "Hey, you-"
By then, Shoichi Kano already had one foot over the bathroom threshold. Scissors formed from her cursed technique appeared in the Slit-Mouthed Woman's hand, and she snipped at empty air.
Snip! The Nokia keypad phone in Shoichi Kano's hand split cleanly in two, paying tribute to the fraud, Gojo, who would fight Sukuna in Shinjuku in the future-after all, he had been bisected in exactly the same way.
Shoichi Kano simply stared blankly at his phone, sparks still sputtering from its severed edges.
By the time the Slit-Mouthed Woman put away her scissors and came pattering over in her slippers, she found Kano holding the top half of the phone in one hand and the bottom half in the other, looking utterly crestfallen.
"Actually..." Kano looked at her. "I never recorded anything."
The Slit-Mouthed Woman pressed a hand to her forehead. "Sweetheart, do you realize how easily someone could get the wrong idea from what you were doing?"
"I think those 'oohs' and 'aahs' Mommy was making were a lot easier to get the wrong idea about."
At a loss, the Slit-Mouthed Woman could only try to change the subject. "I'll buy you another phone."
"Where would you get the money?"
"Never you mind!" She seemed to have a plan already.
After dinner, she really did change into a casual summer outfit, put on a mask to hide the slits at the corners of her mouth, and stroll out the door.
At around ten that night, she tossed an unopened phone into Shoichi Kano's lap-it was even the same model as his old one, just in a slightly different color.
"Where did you get the money?" Kano asked again.
"I told you, never you mind!" The Slit-Mouthed Woman clearly had no intention of elaborating.
In fact, she had just gone out and terrorized some street thugs who were harassing women, farming a little cash off those pieces of human garbage.
Honestly, if she hadn't wanted to avoid damaging the subtle relationship she shared with Kano-something like mother and son, sister and brother, roommates, and lovers all at once-she wouldn't have wanted to resort to such a low-class method either.
The thought that her very first act after obtaining Sukuna's Finger had been to scare a bunch of petty thugs was simply mortifying! A dark stain on her life as a cursed spirit!
"Oh, right." The Slit-Mouthed Woman changed back into her loungewear. "Didn't that woman give us a lot of materials on barrier techniques? Did you take them, sweetheart?"
Kano nodded and took the opportunity to flop into her arms. She held him with a look of disgust. "They're in my schoolbag. You can get them if you want to read them."
So the Slit-Mouthed Woman pushed Kano out of her arms and headed straight for the study.
She tore through the first notebook quickly. After all, her own innate cursed technique included the effects of a Simple Domain, so she easily understood Kenjaku's definition of barrier techniques. She could even extrapolate from the crude barrier techniques mentioned in the notebook.
The later notebooks, however, were much harder for her. When she grew bored while observing humans, she had occasionally blended into the crowds and slipped into schools to sit in on a few classes, but she had never received a systematic education in math or science. Her approach to attending classes had been entirely haphazard: she listened a little whenever a subject interested her, and simply walked out when it didn't.
As a result, she struggled with some of the complicated mathematical and scientific concepts even more than Shoichi Kano did. At least Kano could barely make sense of a formula or two; to her, it was all utterly incomprehensible.
"I'm done!" The Slit-Mouthed Woman snapped the notebook shut. "Time for bed!"
"So Mommy can't understand it either?" A mischievous grin appeared on Shoichi Kano's face.
"Who says I can't understand it?" The Slit-Mouthed Woman came over and pinched the boy's cheek hard. "I'm just... just tired from studying and want a break!"
Kano rubbed the red mark she had pinched into his cheek and asked no more questions.
After that, Shoichi Kano naturally continued going to school as usual. However, whenever the Slit-Mouthed Woman brought him home, he would notice more books on math, physics, and chemistry around the house. At first, they were only middle-school-level books, but later they became high school and even undergraduate textbooks.
Even his desktop and laptop showed signs of use. He found some time to check and discovered that the history consisted mostly of questions entered into search engines.
Then a new kraft-paper notebook appeared beside the black-covered notebook he used to draw lewd pictures and keep his diary.
Kano opened it and found it filled with the Slit-Mouthed Woman's study notes. Her approach was decidedly shortcut-driven. Rather than seeking a systematic understanding, she simply compared everything against Kenjaku's materials and studied whatever she didn't understand. Anything the materials didn't mention, she refused to learn.
As a result, she learned incredibly fast and could even teach some of the material to Shoichi Kano now.
Like right now, for instance.
Shoichi Kano couldn't understand why, after spending all day taking his final exams at school, he still had to attend a barrier technique lesson when he got home.
"A barrier is, in essence, a form of expression of a binding vow. By restricting the conditions of entry and exit, it constructs a 'boundary' that conforms to a specific framework." The Slit-Mouthed Woman had somehow acquired a small whiteboard. She had mounted it on a stand in the living room and written Kenjaku's definition of a barrier on it with a marker.
"Shoichi Kano." She suddenly pointed the tip of the marker at Kano, who was slumped on the couch looking utterly dead inside. "Please explain your understanding of this statement."
Shoichi Kano's mind was wandering somewhere far beyond the room. What understanding could he possibly offer?
So he answered her with a bewildered stare that was as clear as it was stupid.
Thwack! She hurled the marker straight into Kano's face.
"Would you listen to me already?!" Miss Cursed Spirit was clearly a little angry.
Only then did Kano snap back to his senses and hand her the marker that had smacked him in the face.
She resumed writing, speaking as she went. "This statement becomes easier to understand if we look at my own Forced Q&A technique and its accompanying Simple Domain."
She drew a circle, then two stick figures inside it. "Suppose this is my Simple Domain, and the two people inside are me and the target I've selected for my technique. Then the restrictions on entry and exit are easy to identify, aren't they? Obviously, the target cannot escape the Simple Domain until the Forced Q&A stage is complete."
"From the perspective of a binding vow, you could also understand it as me accepting conditions such as being unable to leave the domain or lift my feet off the ground in exchange for preventing the target from escaping the Simple Domain."
"As for the specific framework and the boundary... those are the cursed technique incorporated into the Simple Domain and the 'shell' of the domain itself." She wrote as she spoke, and by now the whiteboard was covered in a jumble of Japanese kanji.
Shoichi Kano nodded repeatedly. Having someone guide him through the lesson really did make it easier to understand.
After the Slit-Mouthed Woman took Kano through Kenjaku's first notebook, the drooling, vacant look on his face gave way to a thoughtful expression.
But even she struggled somewhat with the later notebooks, so she wiped all the writing off the whiteboard and admitted frankly, "I only half understand the later material myself, so I won't teach it in the order that woman arranged her notes. Instead, I'll link together the parts I know according to my own understanding and thought process."
Shoichi Kano perked up and began listening attentively.
Then the Slit-Mouthed Woman sketched the Detection and Protection Barrier she had set up around Kano's home on the whiteboard. "After studying those notes, I made some improvements to this barrier. Now I'll draw a schematic."
"If I explain it using this diagram, you might find it a little easier to understand, sweetheart."
"Let's take this barrier's energy core as the origin, designate this axis perpendicular to the core as the Z-axis, and designate these two perpendicular lines intersecting at the origin as the X-axis and Y-axis to construct a three-dimensional Cartesian coordinate system."
"Then we can express these key energy transmission paths in terms of vectors and coordinates."
"Solving these equations simultaneously, we obtain..."
Shoichi Kano couldn't listen any longer. He fell straight asleep, snoring thunderously.
Halfway through her explanation, the Slit-Mouthed Woman suddenly noticed that he was no longer responding. Only then did she realize he was lying on his side on the couch, fast asleep. She was so furious that she nearly snapped the marker in her hand.
But he was still her own boy, after all. What could she do?
So, puffing her cheeks in annoyance, Miss Slit-Mouthed Woman took her long brown trench coat off the coat hook by the door and draped it haphazardly over Kano. After all, the air conditioner was set very low, and Kano had only just recovered from serious injuries, making him especially susceptible to catching a chill.
Before you continue