University student Ichika Sogawa suddenly inherits five-trillion yen from her father, and attempts are made on her life by her siblings. Her avaricious family made a deal amongst themselves, to let the person who kills Ichika first take all the money, and they try all sorts of means to take her life. To protect Ichika, her housekeeper hires the investigator Hikaru Chikumagawa, who has a perfect record of solving cases before they happen.