|Relatives||Unken Inuzuka (father)|
|OVA||Hot Spring Battle|
|Seiyū||(Japanese dub) Hiroki Takahashi|
Koushi Inuzuka (犬塚孝士Inuzuka Koushi) is the main protagonist of Sumomomo Momomo. His family is associated with dogs. He is the son of Unken Inuzuka.
Koushi is a very handsome teenage boy with short black hair and brown eyes, and closely resembles the image of his father during his teenage years. He is normally seen in his black school uniform. He is extremely popular among the female students of his high school due to his good looks.
Koushi's relationship with Momoko begins with her sudden appearance to his neighborhood. Upon her arrival, she fights with Koushi's father Unken, a very talented man in martial arts and after ending up losing to him, she cheerfully announces her true intention of arrival to Koushi's house; so she could make a baby with him. This strange claim is quickly assured by Unken that when Koushi was born, he and Momoko's father had arranged a marriage between them. Momoko seems happy with this decision and looks forward to have a baby with him. Koushi however, didn't like the idea of being betrothed with a stranger and mocks her as she does not suit for his taste.
At the first of few chapters in Manga, Koushi's had been avoiding Momoko constant approaches of being his bride and her strong desire to have a baby with him. He didn't seem to show any affections of Momoko's attempts, but Momoko takes her role as his 'bride' pretty seriously and is smitten by him; that she does all the chores in his house, such as cooking him dinner, washing his clothes and others without being asked and genuinely enjoyed herself by doing it.
It is revealed that when they were children, Momoko met Koushi once when she was visiting the neighborhood and Koushi saved her from bullies. However, it didn't end up well when Koushi was hung upside down (with his pants down) by the bullies. Momoko got a peek at his 'thing' but she didn't remember that part of the incident and Koushi personally didn't wish her to remember it.
After the Koushi gang ultimate fights with the Koganei clan, the injured Momoko is sent off to her father so that she could recover. While she is away, Koushi could not live properly without her; so much that he had delusions of her cheering him on when confronted by an assassin, his house was a mess and he could not tell the time properly. He seems to grow accustomed having Momoko's around in his 'daily' life and feels lonely and empty without her.
When the newcomer Yuusuke Endou comes to their highschool, he had shown a great interest in Momoko. However, Momoko's only has eyes on Koushi, and didn't entertain his approaches and careful movement to win her heart. The 'normal' relationship between Momoko's and Koushi's turns stern when the two had a fight. Momoko thinks that Koushi didn't care about her when she told him about Yuusuke's invitation for a date in the theme park (after she end up losing to Yuusuke's in their bet) and thinks that the main reason is because of his hatred if being her fiance. She left Koushi and later went on a date with Yuusuke. During the date, she shows her lack of interest towards the date and somewhat seems to sabotage every nice thing that Yuusuke (and his teams) had planned out for her.
At the peek of their date, Yuusuke and Momoko's have been drinking when she keeps mumbling about Koushi-dono under her drunken breath and how she wished that she could spend her time in the theme park with him. Yuusuke loses his patience and angrily exploded after hearing this, had the most intense fight ever with Momoko's and nearly tore up the whole hotel building they were staying at.
Meanwhile, at home Koushi is lazying himself and out of boredom ask the class rep, Sanae Nakajima to hang out with him. Momoko saw him and Yuusuke clouded her judgement by saying Koushi didn't care about her of spending the night outside and rather spends his time with other girls (Sanae). They still haven't talked to each other afterwards and Koushi makes a decision to accompany Iroha Miyamoto to the festivals instead of taking Momoko.
The gang tries to reunite the couple and helps saving Momoko's and Koushi's relationship. They take away his lunch and brought anything left to starve and lure him in so he would end up having a taste of Momoko's cooking (in which he haven't had for days). Although they seems in a good term after Momoko's admitted her faults, it turns out to be pointless when Koushi angrily throw the food on the floor after found out that Yuusuke was also behind it. He angrily left Momoko's in tears but at the same time feeling sorry for his actions. At the end, he regrets his decision and goes back to eating her food while she smiled.
Before his initial meeting with Momoko's, Sanae the class representative has always been by Koushi's side as one of his close classmates. She and Koushi are usually seen studying together and talking about matters related to study and sometimes listening to his problems. They also went out together and he considered her as one of his closest friends. It's not long before it's been revealed that Sanae hold a deep family secret and that is she is the secret protector of the head of Inuzuka clan (Inuzuka Koushi). Nakajima family had been protecting head of Inuzuka clans for generations and the role had been passed down from her grandmother to her as Inuzuka Koushi new protector (her grandmother used to protect Inuzuka Unken). Although Koushi's treated her not more than a friend, she soon started to have feelings for him. However this is strictly forbidden by her grandmother as the role of head of Inuzuka clan protector, she cannot have feelings for him and their job is to be remain under shadows. But she couldn't bear her feelings and willing to break her promise just to go out with Koushi.