Detective Futaro asks the girls what's going on, and they tell him that they don't understand why he's so serious about the test. He tells them that they have a sixth sister, Mutsumi, and that she's in a secret room at the house. He's not sure where she is, but he does know that he can't figure out the answers to the test because they're so different from the answers he'd expected. He says that if the test is a collection of the lowest scores, the culprit will be the one who solves the test the least. The girls agree that the answer sheets are different than they expected, but they also agree that none of them can figure out how to solve the test correctly. Futaro says that he doesn't know who the culprit is, so he'll have to figure out a way to get the answer right. He asks if there's anything to do with the girl he mentioned five years ago, and the girls say that she definitely isn't some idiot like him five . He also says that the girls are trying to set an example for everyone, so they'll do it five times harder.