Iwaki Tomonori is a typical teenager who happens to have a fondness for older women. He nurtures a crush on his teacher but is shattered after discovering her engagement. On his return home, he is taken aback to find Rizel, a 12-year-old girl, waiting for him. The Japanese government has forced a marriage between them with no input from him. It is soon revealed that Rizel is not an ordinary girl but a biochemically engineered human, created by her "papa" creators. Iwaki's parents agree to allow Rizel to stay with them in exchange for having their bills waived. Thus, Iwaki embarks on a new chapter in his life with Rizel.