Onna no Ana (literally, Girl's Hole) is a collection of short stories about boys and girls linked by strange connections at a certain school.
1. Onna no Ana, (Girl's Hole)
2. Onna no Atama, (Girl's Head)
3. Onna no Buta, (Girl's Pig)
4. Onna no Oni, (Girl's Beast)
(Source: Anime News Network)