Not a hentai anime but its from Burst Angel. I don't remember the Japanese name of it.
>>639349she's from Burst Angel.
She's Sai, from Burst Angel / Bakuretsu Tenshi:>
The only good episode. Ep 15 I believe. Everything else after that is full of meh robot and gun action.
>>639397i believe it's spelt Seii could be wrong though
>>639467I believe you're right, and ANN seems to agree as well that it is Sei.http://www.animenewsnetwork.com/encyclopedia/anime.php?id=3560Anime was overall mediocre, if you were going for ecchi it didn't have much of anything.