Clannad (クラナド Kuranado) is a Japanese visual novel created by the software company Key, who also produced the successful titles Kanon and Air. Key released a limited version for the PC on April 28, 2004, and the regular version less than four months later on August 8, 2004. The visual novel was later ported to the PlayStation 2, PlayStation Portable, and Xbox 360. The gameplay in Clannad follows a linear plot line, which offers pre-determined scenarios and courses of interaction, and focuses on the appeal of the five female main characters.
Clannad (TV): Tomoya Okazaki is a third year high school student resentful of his life. His mother passed away from a car accident when he was younger, causing his father to resort to alcohol and gambling. This results in fights between the two until Tomoya's shoulder is injured in a fight. Since then, Tomoya has had distant relationships with his father, causing him to become a delinquent over time. While on a walk to school, he meets a strange girl named Nagisa Furukawa who is a year older, but is repeating due to illness. Due to this, she is often alone as most of her friends have moved on. The two begin hanging out and slowly, as time goes by, Tomoya finds his life shifting in a new direction.
Clannad After Story (TV): A sequel to the recently wrapped anime based on the Key Clannad franchise. After Story is a path that opens in the original visual novel after all the other paths have been opened.
Life continues on for Tomoya. A few months have passed since he confessed his love to Nagisa. Now entering his graduating year, he continues to meet a variety of different people, expanding his own world in the process. As well, Tomoya and Nagisa's relationship begins to enter a level of intimacy unlike before. Through his relationship with Nagisa, and his various encounters, Tomoya begins to understand the meaning and importance of family. Unfortunately, as Tomoya and Nagisa begin their own family together, they are faced with many hardships and challenges along the way.
(source: Wikipedia, ANN)