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Naoyuki Okazaki is Tomoya's father
Naoyuki is Tomoya's father. Tomoya's mother, Atsuko Okazaki, died when Tomoya was little, thus leaving only himself to raise Tomoya.
As revealed from Shino's story about Naoyuki, even though his wife died and he had become depressed, Naoyuki sacrificed everything in his life just for Tomoya's sake, hoping Tomoya to grow up to be a proper man unlike him. After Tomoya comes to understand his father, Naoyuki decides to return to his hometown to stay with his mother, claiming his role as a father has ended.
In the movie, Naoyuki works a night shift instead of staying home and becoming a drunk. He also cares about his relationship with Tomoya and even tries to ease his son's depression in order prevent his son from becoming like him.