Koi no Tyunyu!

From Project-H:
Introducing a collection of amazing hot, steamy sex stories, starting off with a girl mistakenly walking in on a couple having sex. To the boyfriend's surprise, his partner asks the girl to join in on the fun! From then on, he has to fulfill the sexual appetites of two wonderfully demanding women! Another story focuses on the dirty secrets of a girl who is the head of the discipline committee at her school. How far is she willing to go despite jeopardizing her reputation? Other stories include a random fling in the outdoors, a horny nurse, and much more.

1-3. Shinyuu no Kokoroe (Best Friend's Knowledge)
4. A Walk With the Public Morals Committee
5. Futago Shimai no Kyuujitsu Plan (Twin Sisters' Holiday Plans)
6. Omaneki Her Room (Invited Into Her Room)
7. Yozakura no Shita de (Under the Evening Cherry Tree)
8. Hot Motto (Relieved, More)
9. Nurse ni Omakase (Leave It to the Nurse)
10. Take Care of His Friend, Okay?