I've started reading Gleipnir. It's about a boy who finds he has the ability to turn into a mascot-type monster, complete with cute outfit. He hates it but then a rather heartless girl finds out and blackmails him over it. Looks like there are other monsters, too, some of them bad.
I thought I recognized the art style and then when it got to some sexy bits, I realized it was by the artist who did Haru to Natsu, which was a fairly ecchi manga about a guy who was caught between his shy yet semi-yandere girl-friend and her playful and sexy twin sister.