Tomoya Okazaki is the main protagonist of the visual novel and anime series Clannad. Due to his habit of always arriving late to school, skipping classes during the day, and staying out all night, he has been labelled as a delinquent. He is the type of person who thinks deep thoughts about his life, but usually does not voice them out, as stated by Nagisa Furukawa, his main love interest in the series.
He is voiced by Yuuichi Nakamura and Fuyuka Ōura as a child in the Japanese version, and by David Matranga in the English version.
At the beginning of the series, Tomoya is a 17 year old high school student who resents his town because of all the bad memories he experienced while living in it. Rather than falling into depression though, he becomes a sarcastic delinquent. He is a childhood friend of Kotomi Ichinose and is best friends with Youhei Sunohara. As he progresses through high school, he meets many new friends, such as Kyou Fujibayashi, her sister Ryou, Tomoyo Sakagami, Fuko Ibuki, and Nagisa.
Despite Tomoya's sarcastic ways he has a knack for solving the problems of his friends, and seems to care for all of them deeply even if he does not want to admit it. He is also seemingly unaware that some of the girls at school show interest in him or pretends not to know. He loves to play innocent and lighthearted pranks on people; sometimes for his amusement, but mostly to help the victim in realizing his/her mistakes.
Though Tomoya is a delinquent he does not go around looking for fights. However when he does get into a brawl he is shown as a very tough fighter, able to take his opponent's blows and still manage to counter-attack fiercely.
The major story in Clannad is about Tomoya learning about the point of having family and friends, which slowly changes his cynical and negative outlook on life. He also has alternate timeline counterparts that end up with Tomoyo and Kyou respectively in the anime; in the visual novel, Tomoya also has the option of ending up with Fuko, Kotomi, or Yukine.
Ever since his mother, Atsuko, died in a car accident when he was young, Tomoya has been living with his father, Naoyuki Okazaki, with whom he argues with constantly. Tomoya was injured during a fight with his father three years ago; since then, he could no longer lift his right arm higher than his shoulder. After that incident Tomoya's relationship with his father has been very distant.
In the episode On the Hillside Path Where the Cherry Blossoms Flutter, Tomoya met a girl named Nagisa Furukawa while walking to school. Since then, his life changed for the better. Nagisa describes him as someone who is seemingly mean and bad-mouthed, but is actually kind-hearted.
In the ~After story~ saga, Tomoya helps a lot of people like Sunohara, Misae and Yukine settle their problems. His love for Nagisa grows stronger until he eventually marries her after both of them graduate and he gets a job as an electrician, thanks to Yusuke. Afterwards Nagisa becomes pregnant with Ushio. During those months, Tomoya takes care of Nagisa as she grows ill, and once Ushio is born, Nagisa passes away.
Afterwards Tomoya goes into a five year depression, and barely interacts with his daughter, who is left in the care of Akio and Sanae. Later he takes her on a trip, where they meet Tomoya's grandmother, who tells Tomoya about his father's struggles after his wife died. Tomoya realizes that he's putting Ushio through the same kind of relationship he and his father had, and soon becomes a better father. The two of them return to Hikarizaka and he apologizes to his father, as well as introduces Ushio to him. His father accepts and claims that his role as a father is over. Afterwards Tomoya's dad moves back with his own mother, and Tomoya receives an orb of light, only noticed by Ushio.
Later on, however, after Tomoya becomes the true father of his intent, Ushio returns to school and brings together his old friend, Kyou, whose dream was to become a kindergarten teacher during their high school years. Kyou explains that a sports event is approaching. Tomoya and Akio ready themselves for the event with post haste, however, Ushio is struck with the same devastating sickness that took the life of her mother, Nagisa, and Tomoya takes it upon himself to remain with her until the sickness subsides. The sickness does not pass, and Tomoya begins to lose hope. Months later, winter approaches, and Tomoya is still looking after the sick Ushio, who requests to take a trip to the field of flowers
that they'd once entered before. Tomoya, unable to bear disregarding his only daughter's wishes in return for her health, agrees eventually and begins the trip with her. It begins to snow, and halfway on the walk up to the northern field, Ushio collapses, and Tomoya catches her. As he holds Ushio, her last breath being, "Daddy. I love you", Tomoya's daughter dies in his arms, and as he succumbs to the pain and grief of losing both Nagisa and Ushio, he falls into the snow.
After the event that Ushio is revealed to be the girl in the other world, Tomoya, Nagisa, and Ushio are able to be sent back in time, and the robot assisting the girl in the other world turns out to be another form of Tomoya, in the world that ended. Tomoya, in possession of enough light orbs to turn back the hands of time, is taken back to when he first met Nagisa, and reluctantly doesn't speak to her at first out of the belief that it was his doing that she and Ushio died. (Although without him, Ushio would essentially have never existed.) However, in the knowledge that he can change things, and that Nagisa is all he ever wanted, Tomoya doesn't let Nagisa turn away and walk pass him the day they met, and embraces her, discovering that she remembered everything he had. Nagisa tells Tomoya to never regret the time they spent together, and how happy they were. Tomoya returns to the day that Nagisa is in labor, but this time Nagisa survives, as does Ushio, who never suffers the sickness her mother had. This is because the wish Tomoya made also cured her of her disease. Tomoya lives his happily ever after with his daughter and wife.