
Well... I wouldn't really call Suga bisexual since he's not that interested in any other males except Hara. If anything, I would say that he's heteroflexible instead since he's open to the idea of dating Hara who's the same gender as him. (づ ̄ ³ ̄)づ
Yaoi mangaka do tend to prefer to portray their characters as heteroflexible, but I don't see what's so wrong with being heteroflexible. After all, they're still open to relationships with the same sex, having those few exceptions with the same gender seem sort of romantic, don't you think? ^^

Is heteroflexible the new "I'm afraid of being bisexual ?". Because bisexuality means having an attraction to men and women (sometimes other genders too).And that's all it means, it doesn't indicate frequency. You're a man who's only been attracted to another man once ? --> bisexual. Been attracted to mainly men and rarely to women ? -->bisexual.
This heteroflexible stuff screams homophobia/biphobia to me, nothing romantic about it imo.

The thing with the word bisexuality is that people tends to view it in a rather strict way we're you can go out with whoever you fancy. But sexuality is flexible, and there are people who lean to heterosexuality almost completely if not for a very few and very rare exceptions. He is most surely a 1 in the Kinsey scale. Look that up and you'll understand why he isn't bisexual
"I like girls"
Oh really? Why're you so thirsty for your best friend's dick? Do yaoi mangaka have problems with labeling their characters GAY? At the VERY LEAST he's bisexual!