The Phantom Thief and the Female Sage: Magic Vs. Superpowers

The protagonist, Jade, is an ordinary phantom thief. During a job, he is unexpectedly gravely injured by a superpowered person, but is rescued by Lan, a female sage who appears out of nowhere and knows all sorts of magic (and is a total goofball). She then forces him into a contract. After that, superpowered people begin running rampant. To make sure his future jobs go smoothly, Jade asks Lan to teach him magic so he can fight back. And so begins his life of matching wits and battling with superpowered people, alongside his daily life with the female sage... (A lighthearted episodic slice-of-life story with no System.)