I've seen another story like that and they're both guys. As long as the omega has a dick he can fuck anything.
Even girls can get other girls pregnant in this Japanese omegaverse. I just learned this from that Butler Manga Story Something I Can't Remember The Name.
And as long as his swimmers are healthy he can get anyone preggo.
(I have just discovered I have an Omega!Seme, Alpha!Preggo kink).
http://www.mangago.zone/read-manga/boku_no_high_spec_kareshi_sama/
Not fully translated but the raws shows the omega as seme
Since people are saying Azusa might be a sadist i can see the alpha being a total D and then Azusa punishes him by topping him in sex lol Can a omega top a Alpha in the sheets though?