From Bamboo Garden:

Takahashi, Sango, Izmi, Horinochi, and Shinji. The five members to a school group called "Movie Research Club". When the club is to close down, they decide to create a movie as the end-of-the-club ceremony. However, with Izmi not wanting to do it the whole group collides?

Hayato Igarashi has worked together in a Chinese restaurant with Shouko Mishima for a little while. As the reserved Shouko grows closer to him Hayato realizes his greatest wish is to keep her smiling. Will her tragic last relationship stop that? And what'll happen when a new guy comes to eat at the Chinese restaurant?

There's a movie with the same name that came out in 2006 featuring Koike Teppei.

Haruka Nakatani, a boyish girl, transfers into an elementary school where her new class is strictly divided into two groups: girls and boys. But because of this unusual girl, who loves to play baseball, the class atmosphere is about to go through a change as well as Haruka herself...

This is a "Girl's Diary" of four very different girls' lives recorded in four short stories.

1. The O Girl
She tells him that they'll start as "just friends" but he seems to feel differently, telling her that she can't cheat on him?!

2. The S Girl
Always acting as the servant of the guy she likes, Rei-chan is starting to get fed up with this lifestyle.

3. The Girl in the Legend
Just as Tanoko has decided her fate as being only remembered for dying at her school, she meets the most popular guy, who seems to have a problem with being alone...

4. The Negative Girl
All the guys Hinako has dated have ended up in accidents, their lives being almost completely ruined while being with her. Hinako believes that her so-called "negative aura" isn't just coincidence.

From MangaHelpers:
Aoishi Hanae is a 33-year-old woman who has a job, but no boyfriend. In fact, she's also still a virgin. It's not that she never had a chance to lose her virginity, but she let the chance pass by. At a drinking party with her colleagues, Hanae ends up confiding in Tanokura Yuto, a handsome young 21-year-old part timer at her company who also attends college, and who has recently broken up with his girlfriend.
The next morning, she wakes up in a hotel next to him, and learns that they apparently agreed to start dating and then had sex that night. She has only hazy memories, and has no idea how to deal with the situation. Yuto is shocked that she doesn't remember, but hopes that they can still date. How will Hanae, who is older but much less experienced in romance, handle her surprising new relationship with the younger and more experienced Yuto?