It's Okay. Kill Monsters and Upgrade.

This is a boy who traveled to a world of high martial arts and a strange thing happened... On the first day he traveled through time, he found that he seemed to have traveled through time askew. What kind of story will happen when this boy comes to this world? What great waves will this young man create on the mainland? Let's see this time-traveling boy stir up trouble in the mainland. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.