Detective Haika

You're looking for a sad story? Well this anime have sad stories. The story is about Okazaki Tomoya, a delinquent student who skip most of the classes with his best friend Sunohara Yohei, another delinquent. Okazaki Tomoya become close to this guy, because they met in coincidence (or not), and quickly get along. Since Tomoya never like to return to his home after school, he then come to Sunohara's house until night then he return to his home because of he doesn't like his father.

As the story goes on, Okazaki happens to met Furukawa Nagisa on his way to school. They get closer, as far as going to sleep over in her parents place. Nagisa wants to revive the theater club, and his friends like Kotomi, Fuko, Tomoyo, Kyou & Ryou, are trying to help her revive it. When the plot progress slowly, Okazaki later end up with Nagisa, which the story continues in Clannad After Story.

There are also stories in ova/special and movie about Okazaki not end up with Nagisa, but with Kyou/Ryou or with Sakagami Tomoyo. While Fuko and Kotomi's story are not for romance but mostly sad and friendship. Together, Nagisa and Okazaki went through many problems. In the end Okazaki finally find the happy ending after all of this that happens to him.The twin, Kyou and Ryou Fujibayashi's appearance resemble Tsukasa and Kagami Hiiragi from Lucky Star.

Okazaki Tomoya: No big deal. It's just a hill. Why are you unable to climb it yourself?
Furukawa Nagisa: I don't have anything. Even when I go to school... I don't know what should I do. Like happy things, or things that can't be done without me. I don't have anything like that. I can't go someplace where I know I'm not needed.