Arata: The Legend

Arata: The Legend is a Japanese manga series written and illustrated by Yuu Watase. The series follows two boys, Arata, from the mystical world of Amawakuni, and Arata Hinohara, from modern Japan, who switch places. Framed for treason, Hinohara must master a sacred Hayagami sword to save Amawakuni from rebellion while evading his past bully, Kadowaki, now wielding dark power. Meanwhile, Arata befriends Imina, the true heir to Amawakuni's throne, as they uncover a plot to conquer both worlds.

From Wikipedia, licensed under CC BY-SA 4.0.