A tired middle-aged man, Makoto (38, single) was attacked by thugs in a night park and died. Or so he thought, but when he woke up, he found himself in a dungeon in another world! Not only had his body become younger, but he also possessed the power of a spirit mage who could control black flames!! Glad for this opportunity, Makoto bid farewell to his terrible days in Japan and teamed up with Yuuka, a tsundere high school girl with a witch hat who has her own circumstances. Together, they decided to start a new life. Defeating monsters, completing requests, and realizing a slow life! For that purpose—first, escape the dungeon!! "Your job is to protect me from monsters, easy, right?" "What are you expecting from a guy who was almost 40!?" The odd couple of a former middle-aged man and a high school girl, who get along well despite their bickering, aim to become the strongest for the sake of a slow life. A life-restart fantasy begins!!