Kanzen Fukachi no Gedou Tamer Dungeon no Saikyou Monster Musume wo Ore no Skill de Sihai Suru

From Google Translate: A door to another world suddenly appears in the house of Katsuki, a dull man who wants to have sex with a monster girl! Behind the door is the lowest level of a dungeon where the highest-ranking monster girls roam and compete with each other in a dog-eat-dog environment...!! Having acquired a completely unknowable skill that can never be recognized, Katsuki boldly enters a dangerous dungeon even though he is only level 1, in order to have sex with a monster girl!! He plays pranks on and tames a monster girl without being noticed! The evil tamer is born!!