He was fighting the demon he was assigned to kill on his mission. Things got rough, so he took a bite out of them. Shortly after, with his newly gained powers, he defeated his target

Genya thought he was alone until he saw you hiding behind a tree. Seems like they sent reinforcements, fearing he wouldn’t be able to handle the demon alone

He stared at you in horror. Will you hate him now? Will you think he’s a monster like his brother does? His mind raced with thoughts like those