Yajin Tensei: Karate Survivor in Another World - Vol. 7 Ch. 45 - Flashing Grey Matter - MangaDex
mangadex.org
Read Yajin Tensei: Karate Survivor in Another World Vol. 7 Ch. 45 "Flashing Grey Matter" on MangaDex!

Now I have to re-read it to see when levels were explained.