
No, since Kirino identifies as a girl that makes her 100% straight. A straight trans girl. And I don't think it's about seeing the opposite sex naked in general, but just the sheer thought of having sex with a gender your not attracted to, imagining having to touch them, give them oral , penetration, ect was enough to send both Mishima and Kirino over the edge. My poor babes

I think Kirino calls herself gay because it's kind of complicated for some people to understand gender issues. For instance, despite the fact I was born a girl, my heart identifies myself as a boy but I never understood it. I just thought I was crazy. The fact is that I fell in love with this boy for the first time and I thought I was even crazier because I didn't feel we were in a straight relationship, mainly because I'm much more of a man than he is. I feel pretty gay about it all. That's when I got to read this manga and I also found out that one dude I follow on tumblr os gender neutral; it all opened up my eyes for gender issues and I started to read about it. That's when I found out that I'm trans. That's when I found out that I'm kind of in a gay relationship with this boy. So picture Kirino, a person who tries to suppress his trans side, being in such a society like Japanese society, living in the countryside. They have a lot of prejudice against gay people or even non-cis people. It's very xomplicated to understand/accept these kinds of situations... And I'm sorry I really talk a lot Orz sorry

Kirino literally calls herself a girl and uses female pronouns regularly. She even pointed out wanting to become a girl in chapter 6 page 12 and points out that Mishima doesn't use feminine pronouns like she does.
Mishima is a different story though he's a cis gay male with an interest in feminine things (clothing, makeup ect.) He doesn't refer to himself as a girl doesn't show a desire in wanting to become one. Mishima is how you described, just appreciates female things.
So, if a guy identifies as a girl and is sexually attracted to guys, is that still being gay? Also is it normal to throw up if you see the sex you're not attracted to naked? (unless its oral, which makes sense), don't you see way fatter and older naked bodies of both sexes in public baths and beaches and still keep your lunch in?