Responses

Wow, as it happens, the whole "outed by medical attention after clumsy anal sex" part is exactly like the background plot of another yaoi, "12 ji kara hajimaru"...
http://www.mangago.zone/read-manga/12_ji_kara_hajimaru/

The. Why did he give uke a bj?
My guess...
I'm going to guess that when he was in high school he had a boyfriend. They tried to have sex but being young and inexperienced the janitor guy accidentally hurt his lover.
The lover ended up needing medical attention and was too embarrassed to admit the sex was consensual.
This is my guess how for how the whole 'in jail for rape' scenario played out.