Mineta Chisato has not lived a normal life for the past two years, constantly on the run from her father's debt collectors. On one particular day after being cornered by them, Chisato is rescued by Ookura Shinzou, a wealthy inventor, who shockingly says he'll pay off her debt of 100 million yen. But there's a catch -- he's convinced he only has a month to live, and she has to be his wife for the rest of that time. Oddly enough, Shinzou does in fact die after a month, and Chisato mourns, but is ready to move on with her new life. However, it seems there were a few stipulations in the fine print of her marriage contract, and she's suddenly forced to move to the family mansion, Trick Heart Castle, and play mother to Shinzou's six adopted sons.