OMG
Suzuya Juuzou – He’d be intrigued. A bit confused as to why he chooses certain things. But I think he’d be happy that he’s found friendship and happiness, and that Mr. Shinohara still matters to him.
Shinohara Yukinori – He’d be disquieted at his vegetative state. He would, however, ask about whether his family visits, how they and Suzuya are doing, etc. Once he finds out they’re okay, he’d be more accepting. And he’d be very intrigued by the ghoul who visits to bring him flowers.
Houji Kousuke – He’d be very disappointed about what happened to Seidou. He’d even debate with himself whether he should have tried to kill him. His :re self will insist on killing Seidou now, Luke-Skywalker-to-Ben-Solo style. But he won’t be able to do it, not yet.
Takizawa Seidou – He might go a little crazy. He’d deny it flat-out. “There’s no way you are me, goth freak!” And then he’d cry and spend more quality time with his family and Rocky. He’d probably keep it to himself, though. His only way for calm would be denying it and occasionally reminding himself that Akira and Amon did not reject him even then.
Mado Akira – She’d be intrigued, though the idea that she’d befriend the Rabbit and Yotsume would offend her. She’d also be interested in stopping Seidou and Amon from becoming ghouls, which might cause problems. Amon might then wonder why she kept bringing him donuts every morning.
Amon Koutarou – He’d be sickened that he’d turn into a ghoul. Once he realizes he can still be a good person and help his friends, as opposed to being the predator Donato was, he’d calm down a little. In time, he’d realize that knowing ghouls and humans are connected far more than he imagined is freeing.