Saigō is a large, muscular young man who attends the same school as Kōshi and the rest of the main cast. He has a very threatening demeanor, communicating mostly in grunts and gestures and continuously wears sunglasses. He is the admired leader of a trio of hoodlums from Kōshi's class and apparently frequently gets into fights. Appearances are deceiving, however; Saigō is quite fond of kittens, of which he has several, and apparently reads romantic stories for enjoyment. When he first meets Alice Uzuki, he defends her against a large group of assassins without any concern for his own safety. Later, he takes a hit from Alice's guitar string weapon to protect Kōshi from harm. He falls deeply in love with Alice and seeks help from Momoko and the other main cast to find a way to deepen their relationship.

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? 
(Source: Kotonoha)

Momoko is the only child of the Kuzuryuu clan, a powerful martial arts family with inhuman strength. But strong as she is, her father fears a woman will never be able to master the skills of the family. Unless Momoko marries and bears a capable heir, the Kuzuryuu line is doomed to weaken and die off! With this mission in mind, Momoko is sent to the rival Inuzuka clan, where she is to marry the son of their mighty leader. But Koushi Inuzuka abandoned the martial arts long ago. Now committed to his legal studies, the last thing Koushi has on his mind is marriage &mdash; especially not to the world&rsquo;s strongest bride! 
(Source: Yen Press)

Katsuyuki Saigo