The Mad Wind Mage - S1.E21

Since the new Pandemonium appeared, battles held every night which pitched "magicians" together in a battle and the winner gains experience points. Kazuma appears at these battles, brutally attacking the combatants and asking them on the location of Pandemonium. He goes so far as to assault Katherine and allow Nanase to be kidnapped. Afterwards, Tachibana informs Ayano that Kazuma has regressed to his former cold-hearted persona, and only Ayano can bring him back.