@HolyOrdos
If you mean him questioning why he's concerned about the dude asking Erika out, I think it makes some sense here. He likes Segawa, and is trying to get with her. Even if we as the reader realize that this is a love square, his wishes and desires currently are to get with Segawa.
And I dunno about you, but when I was a teenager, when I had a huge crush on a girl, if I felt anything for another girl, I felt a bit guilty because I was supposed to "be in love" with the girl. He probably doesn't even consider the idea that he might get together with anyone other than the person he considers himself to be in love with and who he plans on spending his whole life with, despite still being in fuckin high school.