High schooler Yūta Iridatsu has experienced “astral projection” i.e. his spirit has been separated from his body. He woke up in a mansion named Koraikan and met a cat spirit named Chiranosuke, who told him “You must find the Sacred Tome of Koraikan in order to return to your physical body.” While searching through corridors of Koraikan, Yūta bumped into underpants of its female residents, and doing so would, eh, create some big trouble for planet Earth.

If he sees underwear, humanity will be destroyed!? An original anime series from the noitaminA block, Punchline centers on Yuuta Iridatsu, a high school student, with a peculiar habit. When he sees a girl's panties, he gets so excited he faints! After a certain incident with a ghost cat, his soul gets separated from his body. Using his special powers, Yuuta watches the daily lives of the inhabitants of an apartment and sometimes plays tricks on them. Eventually, Yuuta decides to unlock the secrets to why Earth will be destroyed and tries to save it!