The only ending for this manga that is acceptable is for Naoto to get turned into a woman and passed around to all the guys where he gets all their skills but ultimately ends up a cumslut so he can finally NTR himself.
So the real question is, will the author have the balls to make Ekoda-sensei pregnant from her tryst. Sure, it doesn't always happen in one go, but this is a manga after all so anything goes.