[MisaoFan]

If you like ecchi, romance and fantasy, I suggest you watching Qwaser of Stigmata. It's full of action, has decent amount of high-level ecchi. Most of characters (except Sasha who was a 13 years old male protagonist and Katja, a 10 years old loli sadist) are 15+ aged characters.
You can also check out C3 -Cube X Cursed X Curious- : it's about a highschool boy who meets a cube in a form of a human girl who was formally tortured in the Middle Ages. It's a dark harem fantasy who contains a healthy dose of romantic comedy. Every characters (even the cursed tools who were 100-ish years old, even though they have a younger appearance) are 15+ aged characters. The same goes for Is This A Zombie ?, a lighthearted ecchi romantic comedy who also possess a dark side of zombie fantasy and magical boy (male equivalent of magical girl).

For the romantic comedy titles who were devoid of action, check out R-15 : it's about a 15 years old boy who works as a erotic writter. Despite being popular, he was feared by every teenage girls. One day, he enters a academy where only geniuses can be accepted and met a young, shy flutist. The embarassing adventures starts badly for him !

You can also check the upcoming Highschool DxD (waiting for english subs), an highly ecchi dark harem fantasy about a boy who gets killed by his girlfriend before being ressurected as a devil by a powerful devil girl.