Are You Willing to Fall in Love with a Pervert, as Long as She's a Cutie?

After cleaning the Calligraphy Club room one afternoon, Kiryuu Keiki found a love letter addressed to him on the club's desk. Eager at the possibility of finally getting a girlfriend, he opens the envelope only to find the words, "I like you" along with a pair of the sender's panties. With only these panties as evidence, Keiki narrows down the identity to the four girls who helped him clean the room.