I didn't like Groupie or White Brand, mostly because of the reasons you mention. I do believe that threesomes can end up happily in love, but apart from Hasta la Vista, I don't think any of them are believable. The stories in White Brand doesn't leave much of an expression as they are so short. I find that stories about very young protagonists doesn't do much for me, hence my indifference towards school stories. I am too old to care. :D

Groupie... the whole story puts me off. Not because of the incest, not because of the threesome, but because the characters seem superficial and not real, this is definitely not Nitta's best work. When that's said, I'd rather read White Brand and Groupie than most other manga. It is still a quality story with good drawings. But they'll never become my favourites.

Tomomi/Yoshizumi? Why not? Yoshizumi is the little black dress of YN fandom, it seems. We need to have a Yoshizumi-month and try to pair him up with a lot of interesting guys.

(And OMG! there is nothing better than mating-bond Snupin. All Snupin should have that!!! ♥)