so everything miki told tatsumi was a lie? even the flashbacks about miki and his supposedly sister's childhood and when miki was assaulted by the supposedly husband? but he did cry when tatsumi asked him, right? if those were fake then why did he cry???
okay, but then what about his "sister's" child? the author somehow implied that miki was the father by saying the child "was born 10 months after the incident", and also about the "sister" "she's probably well-versed in lying too". even if that's not the case, there must have been something hidden...
Then why did, Tatsumi, the guy that ended up becoming delusional, asked Miki's ghost who the father of the child was? If we are supposed to believe that it was reincarnation why would Tastumi ask such a question when he saw the child who resembles Miki so much? I think the person above had a point in commenting that Miki most likely had an affair with his sister and her husband found out about it which was why he ripped out Miki's nails. And which is also why the child looks so much like Miki.
Be kind and share your happiness