Aye, this is an awesome anime/manga about a teacher and his students. The situations are completely normal, but the characters are beyond awesomely strange. Here's a quick list of the characters...
Teacher (Nozomu Itoshiki):
Mr. Despair himself. He is a man who can only see things in the most negative way. Regularly tries to kill himself. Fails every time.
Students:
Kafuka Fuura: A girl who can only see things in a positive way. When Itoshiki tries to hang himself, she claims that he was only trying to make himself taller.
Chiri Kitsu: If ye know what an OCD person is, this is that to the extreme. EVERYTHING must be neat, orderly, and equal. She seems to have a butcher knife and a shovel for some weird reason...
Kiri Komori: A hikikomori, or someone who has completely isolated themself from the rest of the world. She seems to hide in some weird locations sometimes. Also, she's really cute. ;o;
Matoi Tsunetsuki: The most insane stalker I have ever seen. Does not need anymore description.
There's a lot more, but it'd be easier for ye to just see em and find out for yeself. The series is mostly comedy with some freaky bits thrown in. It's also a tad bit on the mature side, so I'd only recommend it to people 16+.
And with that, a scene from the show...
