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Tomonori Iwaki is a 15-year-old student who likes older women. 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", of course). 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.