You have come to Tokyo to take an entrance exam. You are staying at a relative's house, which you are not very fond of. The reason why you are not fond of it is because the four sisters in this house are extremely "damn serious". When they find out that you are taking an exam, they are in trouble, and of course they start cheering you on in the "wrong" way. If it's cold, they warm themselves up naked, come to wash their bodies in the bath, and collect all of your sperm so that you can concentrate... With all their support, you will definitely pass.