Key Club is a brand of ビジュビルァーツ (Visual Art's). It is a game production company in Osaka, Japan, and is famous in the industry for making touching AVG (electronic novel game). Key's most famous four seasons trilogy-Clannad in spring, Air in summer, One in autumn (the original production company was Tactic, but the production team was mainly the producer who later joined Key), and the girl of snow in winter. Key's game story is full of fantasy and warmth, and its tense plot always makes people cry, which is why Key's game is called "crying game". Because Key is also called "Key", key and Leaf are often called "key leaf" or "leaf key" among fans (the latter is mainly used online). The key fans are called "Key".