Responses
he's line = his line (typo error)
That's not what psychosis is. His only delusion is thinking that what he's doing is excusable, but that isn't psychosis. If anything, he has antisocial personality disorder for being unable to sympathize and having a complete disregard for social rules and personal boundaries.
This story makes me feel like "I'm a helpless person". I though the uke/older brother was a lawyer too like his sempai or maybe he's just working in his sempai's law office but still he was a law student before and I still don't get it why he's line/flow of thought is someone who was always or easily oppressed. Character-wise, I think the older brother has a flat character unlike the little brother who was fully-developed (suffering from psychosis). Anyways, I think the most reasonable man in this story is the doctor.