On his very first day in Japan, Sherlock had received far too much information. Setting aside the fact that a Japanese version of the Death Eaters, Monster Mountain, was watching him hungrily from the shadows, there was also the Demon-Sealing Gate, which Japan's greatest wizard in history, Abe no Seimei, had used to seal demons and monsters—and which truly lay beneath Mount Fuji. Sherlock had even been fortunate enough to see its ruins.
Then there was the Doman Manuscript in Sherlock's possession.
Yes, he had still kept the Doman Manuscript on him. Teramoto Shoma would arrange for men to escort Sherlock back to Britain tomorrow. In truth, no escort was necessary—given Sherlock's current strength, leaving Japan would be easy enough—but Teramoto Shoma insisted that the proper courtesies had to be observed.
When he wrote the invitation letter to Sherlock, he had never intended for Sherlock to come all the way to Japan to personally study and break the magical protections on the Doman Manuscript. Rather, he hoped to entrust it to a powerful wizard in the modern world who would be difficult for other forces to threaten. In Teramoto Shoma's eyes, Sherlock was the most suitable candidate.
Teramoto Shoma also admitted that if Sherlock had refused to come to Japan, he would have written to Dumbledore instead. And if Dumbledore had refused as well, the Great Way Academy Shogunate would rather destroy the Doman Manuscript. Even if its secrets were never revealed, they would never allow it to fall into Monster Mountain's hands.
Sherlock was somewhat surprised that he had apparently been ranked ahead of Dumbledore.
The reason Teramoto Shoma had insisted that Sherlock personally come to Japan and take the Doman Manuscript away for safekeeping was that he feared there were Monster Mountain spies within the Great Way Academy