A high school in an unidentified Japanese town serves as the setting for Clannad. Third-year student Tomoya Okazaki doesn't take school very seriously. His peers, who are occupied with studying for their university entrance tests, view him as a persistent nuisance because he is constantly late. He has few friends there as a result of this.
However, Tomoya doesn't seem to worry much about this until he meets Nagisa Furukawa, a girl who similarly doesn't have any friends because everyone she knew had left school. She seems quite awkward and dim at first, but he can't seem to get away from her, and as he helps her, he meets more and more schoolgirls. He initially shows little interest in them, but as they get to know one another, he gradually begins to open up.