Yo and Yomoto. Portal to Kinko

Yo – an ordinary schoolboy. He loves manga and admires his favorite character Yomoto.

A fearless ninja superhero who is unbothered by anything. Their worlds were never meant to intersect, but Yomoto suddenly finds himself in Yo’s closet! The real one!
Now the friends have to hide the truth, invent legends so that the Japanese ninja can attend a Hamburg gymnasium.

In the guise of a cool "exchange student" Yomoto repeatedly helps his new friend out of school troubles.

However, it's strange that the ninja is in no hurry to return home. When Yo uncovers his friend's secret, there is very little time left: they need to travel to the world of manga to save the village of Kinko, Yomoto’s home, from destruction