Yuusha no Katsuyaku wa Korekara da!: Isekai kara no Demodori Yuusha wa Heion ni Kurashitai The Hero's Success Is Now!

Synopsis

Tatsuya Mikage was summoned to another world to fight the Demon Lord reluctantly. After years of effort, he returns to Earth with an assassin girl named Henry and a Peach Dragon to find that 15 years have gone by and his parents have already passed away. Now without a proper education or connections to modern Japanese society, Tatsuya now lives using his alchemy cheats to make a humble living.