Responses
You are right about Masayuki... About Keisuke, it seems to me he had none sexual experience and had never fallen in love before... so I think he just didn't knew much about his sexual orientation... but he may be bisexual
Masayuki is a kinky ikeman heterosexual who is a stray (Straight guy turned gay) at the end of the story? The other guy, Keisuki, is also stray?