I Got a Cheat Skill in Another World and Became Unrivaled in the Real World Too Vol 7 manga

Description:

Princess Lexia’s older brother, Reigar von Arselia, was poised to inherit the throne. At least he was...before tragedy struck. Now, Reigar’s heart has been twisted by madness and plunged into a darkness so deep, a black hole would feel bright by comparison. What will happen when the Vile girl pulling the strings and bending Reigar to her will comes face to face with Yuuya—who now possesses the power of a saint!?