Juni'ichi Nagase is a high school sophomore who saves new student Yuuhi from harassment, only to find out that she is to be his future wife!

Yuuhi Katagiri is not your average girl - she's the treasured daughter of the Katagiri family. She's generally kept under strict supervision, but one day ends up walking home from school on her own. This proves to be instant trouble when a group of boys start harassing her. Junichi Nagase, who was on his way home from a convenience store, sees the troubled Yuuhi and comes to her rescue. One of the boys recognized Junichi as the famed "Geno Killer" and they dash off. Yuuhi thanks Junichi and when she asked for his name, he just waves and leaves. Of course, he regrets trying to act cool in front of the beautiful girl right away, wishing he asked her name. The following day, a transfer student joins Junichi's class - it's Yuuhi. She calls Junichi out as the "Geno Killer", the only name she remembers him by, and rumors about the two spread quickly. Matters are made worse when Junichi kisses Yuuhi due to a misunderstanding. And on top of all that, it turns out that Junichi is Yuuhi's fiancé. Yuuhi doesn't see Junichi as someone worthy. But, she could not go against her father's wishes. The only thing that Yuuhi can do is live with Junichi in the house he shares with his little sister Minato, and prove that Junichi is not worthy to be her husband. Will she succeed in proving his unworthiness, or will she fall in love on the way?—MyAnimeList

Junichi Nagase was a real delinquent in middle school, one nasty enough that he earned the nickame "Geno Killer," and it's by this less than flattering epithet that Yuuhi Katagiri first comes to know him when he rescues her from two thugs one evening. Needless to say, both are stunned when not only does Yuuhi find herself transferred into the same high school class as "the Killer," but that shock grows into outright stupefaction when Yuuhi shows up at Junichi's house with the mind-blowing announcement that she's supposed to move in with him. It seems that they're engaged, and since this is the first that Junichi and his younger sister Minato have first heard of the arranged marriage set up by their parents, it's an idea that's going to take a little getting used to. Get ready for ties that bind and gag as bad boy and good girl collide cohabitationally while the entire school gets to watch. Truth IS stranger than fiction in Akane iro ni Somaru Saka.—Sentai Filmworks

On his way to school Junichi Nagase saves a girl from danger. Later due to a misunderstanding he kissed her. Shocked and disgusted, and without understanding what just happened or why, she screams at him and tells him to "just die!" As it turns out, the girl, Yuuhi Katagiri, is a new transfer student and, much to the surprise of Junichi and his younger sister Minato, their father arranged for Yuuhi to be Junichi's future wife. Of course, getting married to "that perverted idiot" is the absolute last thing Yuuhi wants. Junichi's crazy school life with his tsundere bride-apparent has begun.—Animesuki

One day Junichi Nagase comes across two boys tormenting Yuuhi Katagiri. When he steps in to help they run off calling him "Geno Killer". He then walks off without introducing himself or allowing the girl to either. The next day to both of their surprise she is introduced as a new transfer student to his class. The following day due to a misunderstanding he kisses her which greatly upsets her. That evening to his surprise and dismay she shows up to his door saying she is his fiancée and that she has come to live with him to evaluate him to see if he is worthy of her. Much hi-jinx ensues as the days go by.—Anime News Network