Sumomomo Momomo: Chijou Saikyou no Yome

Momoko Kuzuryuu is a martial-arts crazed teenage girl who has grown up in the mountains with her father, a legendary fighter. However, one day her father tells her that because she is a girl, she will never be able to master the family’s ultimate technique. The only thing for her to do is go marry the strongest warrior, and produce the strongest offspring. Her unlikely fiance is the handsome but weak Koushi Inuzuka, the son of her father’s best friend and rival. Their marriage was agreed upon by their fathers before they were born. However, Koushi has no interest in martial arts; in fact, he is a coward who freezes whenever he sees violence. Instead, he wants to become a prosecutor, so that no criminal can escape capital punishment. Despite Koushi’s adamant refusal to marry her and his subsequent displays of cowardice, Momoko falls in love with him and swears to remain in his house and train with his father in order to become the strongest fiancee ever.

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Koushi Inuzuka is a smart high school student who aims to become a public prosecutor. Unfortunately for our good guy, he was born into a martial arts family whose head (ie his father) only knows one language: violence. When Koushi was still a baby, his father made a pact with his biggest rival to marry Koushi to his opponent-turned-friend’s daughter. The union of the two blood lines is supposed to bring forth Earth’s strongest martial arts clan.
Skip forward: Koushi is in high school, oblivious to the marriage arranged for him at his birth. Enter Momoko Kuzuryuu: sugar bomb, airhead, loli martial arts artist and Koushi’s self-proclaimed bride (the strongest on Earth, no less). Her wish for sexual intercourse meets with Koushi’s square refusal as he has absolutely no desire to get it on with someone who looks like she could be his little sister, not to mention that he doesn’t have the foggiest idea who she actually is.
Meanwhile, a war has broken out between the martial arts families. For Koushi, this means that numerous fighters are out to challenge/assassinate him. As if that weren’t bad enough, our protagonist also has a fight phobia due to a traumatic incident that took place in his childhood. Now it’s up to Momoko and her superhuman fighting skills to protect her “husband.” Will the two sweethearts survive the trials and tribulations ahead of them? More importantly, will Momoko get her way receiving a baby from Koushi?