Oibore Yuusha no Isekai-go

The manga is set in a fantasy world that has vanquished its evil lord and gained peace 60 years ago, and now the hero that led the band that saved the world is in dire straits. Now in retirement age, he is as powerful as ever, but has forgotten so much. The country's leadership is troubled about how to manage the hero, but a certain incident puts him and a maid to tour the world. (Source: ANN)