Responses
I was confused too. I had to check the email from Blonde Hisashi, and got that they had different surnames.
I think Iljima kinda somewhat abused him since Chii had bruises then Shinoda also rejected him. Nevertheless, their past is twisted and Iljima could possibly a really horrible guy.
Ok this confused me at first but I think I got it right:
Shinoda Hisashi is Chii's childhood friend and unrequited love of many years.
Ijima Hisashi is shige-san's work friend who Chii met after moving to Tokyo to get away from his hopeless crush.
Now I can't tell if Ijima knew about the other Hisashi or not but I'm thinking he did and used it to manipulate chii into having sex with him. Chii, still loving his friend back home, agrees because their names are the same and he wanted to somehow simulate having sex with "Hisashi"
Now, the real reason why Chii was so damaged hasn't revealed itself yet so I can't say anything about that but I'm guessing the phone call at the end was Chii telling Hina either everything or that he was breaking up with him. And wth the return of ijima, everyone is on edge.