...a sex-changing manga (e.g., Ranma 1/2) where the LI turns out to be bi- or pansexual? It seems like it would be a fun twist on the usual confusion to have the LI go, "Oh, you're a boy AND a girl? That's cool." (It's probably been done in doujinshi, but I haven't seen one in an actual published title, at least not in translation.)