Ayakashi Tenma

Himeka Tenma, a sixth-grader in the Amatsu Little League baseball team, is suddenly transported to Mount Kurama during a baseball game in Kyoto. There, he finds Mikazuki, a Kukuri (a yokai user), battling a Karasu Tengu with a giant snake. The Karasu Tengu is eventually bound by the snake, and Tenma is told by Mikazuki, "Don't see, don't hear, don't know about everything that happened here," before he leaves. That night, Mikazuki appears at the inn where Tenma and his friends are staying . He had forgotten a talisman of Fudo Myoo when he met Tenma earlier that day. At that moment, a celestial star appears outside.

(Source: Wikipedia, translated)