Okay, okay. So Nanami is the older sister but during the different situations he got removed from his own family ties, and Mana (Who feels like a new character but I might be mistaken) was a childhood friend like Okiku whom he feels guilt for and hates himself for not being able to save her. Also he is making assumptions about why he isn't with his family now, but will probably be cleared up in the following chapters. I am also not convinced Mana is actually dead. I appreciate the Tls.