Second season of Osomatsu-san.

Wei Ran, a college graduate, was accidentally led into a world he never thought existed by a cat. When he was trying to find a way to return home, he learned that the only train that could take him back to the human world would only arrive in half a year. He could only temporarily live in the shop run by Mao Mao Yaya - Guaixiang Sale. Just when life seemed to be settling down, Wei Ran unexpectedly discovered that no matter where he went, dragon scales would appear. And every time the dragon scales appear, it causes completely different strange effects...

Kyuu is your average boy with a knack for logic and reasoning. Desiring to become a detective, he finds out about the existence of the Dan Detective School (DDS); a famed school where students are allowed to bear arms. Together with Megu, a girl with photographic memory, the martial arts master Kinta, the genius programmer Kazuma and the mysterious Ryuu, Kyuu tackles many well planned out crimes, always seeking the truth.

After the defeat of the demon lord Hadlar all of the monsters were unleashed from his evil will and moved to the island of Delmurin to live in peace. Dai is the only human living on the island. Having been raised by the kindly monster Brass, Dai's dream is to grow up to be a hero. He gets to become one when Hadlar is resurrected and the previous hero, Avan, comes to train Dai to help in the battle. But Hadlar, announcing that he now works for an even more powerful demon lord, comes to kill Avan. To save his students Avan uses a Self-Sacrifice spell to attack, but is unable to defeat Hadlar. When it seems that Dai and Avan's other student Pop are doomed a mark appears on Dai's forehead and he suddenly gains super powers and is able to fend off Hadlar. The two students then go off on a journey to avenge Avan and bring peace back to the world. (Source: ANN)