Isekai wa Smartphone to Tomo ni.

Touya Mochizuki dies because of a careless mistake made by God, who apologizes by reincarnating him in a fantasy world with enhanced abilities and one personal request. Touya asks to keep using his smartphone. It cannot contact Earth, but divine modifications give it access to maps, information, and a power supply that never runs out.

The phone quickly becomes only one of Touya's advantages. He has an extraordinary affinity for magic and soon gathers friends while traveling through kingdoms filled with monsters, ancient ruins, political problems, and convenient opportunities for adventure. Touya is powerful enough that most obstacles become unusual puzzles rather than desperate battles, leaving plenty of room for friendships and romances to grow around a boy who entered another world with the most modern tool imaginable in his pocket.