YunaGreyworth's manga / #Frog Magician(1)

Ore to Kawazu-san no Isekai Hourouki

Ongoing | Kuzumochi,Ryuu | 2000 released

MC was summoned by the strongest magician to be his successor before dying. After discovering his overkilling magic power level, MC managed to revive the old man but as a frog. And thus start their cohabitation in a magical world.