Kyoukasho wa Oshiete Kurenai

From Which Scanlations:

1. Kyoukasho wa Oshietekurenai

2. Toumen na Jikan
Normally, people who have died haunt their lovers or their enemies... So why is Yuuri, the ghost of a high school girl, following her boyfriend's little brother around?

3. Kanojo no Tabako

4. Okubyou na Kimi no Te - The Untouchable Venus
Shino thought she could drive away the persistent Takeomi by telling him that she didn’t want to do anything physical–even hold hands–until she was married. But he agreed, and the two of them had a good relationship until Shino’s first boyfriend showed up and revealed the real reason why she was “waiting”.

5. Kyoukasho ni wa Notte Inai
"In high school, our responsibility is studying... But isn't it also important to learn about love?" Hinokawa wants to know the things that can't be found in a textbook--but the teacher she's chosen to focus her affections on isn't exactly responding the way she wants him to.