Mitsuki, a schoolgirl, visits her classmate Kenta's house but nobody answers when she rings the doorbell. As she tries to leave by putting some prints in the mailbox, a man named Gundam appears. He claims to be Kenta's father and calls his own son a "bad kid." Angry at his words, Mitsuki ignores Gundam's protests and enters Kenta's room. There, she finds Kenta waiting for her and he forces himself on her...