The storyline of Rizelmine centers on Tomonori Iwaki, a 15-year-old student who likes older women, including high school girls, college girls, and even female instructors. Having just discovered that his teacher (upon whom he has nursed a massive crush) is engaged to be married, he comes home to find, much to his dismay, that he has been forced by "Power Of The State" to marry a 12-year-old girl named Rizel, who is the government's first creation in its experiments to genetically engineer a human. Whatever resistance Iwaki's parents might put forth is immediately dissolved by promises of free HVAC, promotion, and government paid home loans, all instituted by "Power Of The State". Despite Tomonori's protests, Rizel and her three secret service guardians known only as Papa A, Papa B, and Papa C move briskly into Tomonori's house, and the stage is set.

Rizel's tears contain the same make up as nitroglycerin and as such are explosives which creates a need for constant repair in their house. A running gag is that at the end of each episode, Tomonori calls Rizel an idiot, causing her to cry and thus cause an explosion. Rizel, with the help of her Papas, tries as hard as she can to win Tomonori's love. However, Tomonori is still in love with his teacher. Other characters creating an ever-tangled love web are Ryunosuke Hououin, who is in love with Rizel, and Kyoko Yachigusa, who is in love with Tomonori. Both try their best to prevent Rizel and Tomonori from getting close to each other. Later on Tomonori finds out that Rizel is the older woman he fell in love with when he was young but she was unable to grow after they met because she fell for him too, and she needed more than just the love from her "papas". When he learns this, Tomonori realizes that Rizel is his older woman.

Rizelmine (りぜるまいん, Rizerumain) is a manga series written and illustrated by Yukiru Sugisaki. The manga was originally serialized for six chapters in the Kadokawa Shoten magazine Ace Next from November 2001 to April 2002 with a single tankōbon collection released on March 22, 2002. The manga has was translated into English and published in the North America by Tokyopop on August 9, 2005. An anime adaptation co-produced by m.o.e, Imagin, and Madhouse aired on Japan's Kids Station in 2002, but has not been licensed in English. Rizelmine was split into two seasons, both containing 12 episodes each. The first season aired April 2, 2002 through June 18, 2002. The second season, titled Rizelmine II, aired October 5, 2002 through December 21, 2002.