[Quarkboy]

I've read the first manga volume and all the characters so far are straight.

However style of the manga is clearly influenced by some BL tropes, especially the uke/seme relationship.

But it's done in the context of a budding _friendship_, not a budding romance.

I.e. it'll be fodder for BL doujinshi, but there's no actual BL in it. As for the anime, that aspect could easily be de-emphasized by directorial decisions.