Akihime didn't go where Yukimura wasn't, so she stayed close to the school as well. They had grown out of their silly teen embarrassment of dating and became open about it at graduation. Despite what they thought, no one thought less of them for it. It made her happy, knowing she could be public with her feelings about him.
Mitsunari did not stay on campus, however. He stayed at the Otani household, as was demanded of him as the oldest. He taught under his most trusted tutors so he could assume the role as head.
Masamune, on the other hand, was scheming. He had been toying with the idea for years, and he was thinking now was as good a time as any to enact it.