Huh!?...I though that Yue wears only adult sexy underwear because it's easier to take off when she goes to the toilet...sight...that plain pantsu she has in the picture doesn't feel right.
no, Shinjidude was right, a little into the second manga they play a game called "baseball janken", which is basically a study session where you have to take off one article of clothing for every wrong answer. so basically a strip poker of sorts
