Here is another anime based off of an H-game back in the late 90's. It has an interesting concept of a Touya Fuji who's girlfriend, Yuki Morikawa, is an upcoming idol in Japan and deals with the stresses of having a girlfriend of her status. Along the way he is involved with Rina Ogata, another idol who is also friends with Yuki. A love triangle ensues itself etc. etc...

One of the main reasons I like this is because two of my favorite seiyuus are in the same anime: Nana Mizuki AND Aya Hirano! XD
Aya Hirano voices Yuki and Nana Mizuki voices Rina.

Here are some character songs of Yuki and Rina
Yuki's song-White Album

Rina's song-Sound of Destiny