Negattemonai Tsuihougo kara no Slow Life? Intai shita Hazu ga Nariyuki de Bishoujo Gal no Shishou ni Nattara Nazeka Mechakucha Natsukareta

Reito Harukaze, who had climbed to the highest rank of adventurers, had retired. One day, as he was thinking of living a quiet, retired life, a beautiful gal named Karen Hiiragi appeared before him. "Hey, mister, buy me a meal!" Upon hearing that Karen was in trouble with money, Reito decided to give her a basic lecture on dungeon conquering. "Thanks to you, I was able to conquer my first dungeon! Master!" He actually wanted to retire and live a slow life... (Source: Kadokawa, translated)