Ruca, trapped under a rock, is saved by a man dragging a large sword along the ground. Coming from Brazil to Niigata, she offers him a drink from a pokan juice. Why does he drag this large sword and how does the earth turning into a vast desert land relate to him?

The father of high school student, Katsuragi Yako, has been murdered. A cruel murder. The incident filled with mysteries drives Yako's daily life into confusion... As the investigation progresses slowly, a man named Nougami Neuro appears before Yako saying that he wants to eat the ultimate "riddle"...!! The Demon Neuro has a raging hunger for ‘mysteries.’ Being dissatisfied with his current regime in hell, he’s come into the mortal realm in order to satiate his ever-growing appetite. The murder case of a young girl’s father seems to be sufficiently enticing for the Demon’s needs... But what else might happen between these two? Find out in this disturbingly good murder-mystery series.

The story is about class 3-E of Kunugigaoka Middle School where every morning they greet their sensei with a massive firing squad. The sensei is a weird combination of an alien and a octopus that moves at speeds of mach-20. It turns out this creature was responsible for the destruction of the moon, rendering it forever in a crescent shape. He has announced that he will destroy the world in one year. The creature will teach class 3-E how to assassinate him before the year is over.