100-nin no Eiyuu wo Sodateta Saikyou Yogensha wa, Boukensha ni Nattemo Sekaijuu no Deshi kara Shitawaretemasu @comic  

Eisen was instrumental in saving the world from the evil god by raising 100 heroes. Despite sustaining severe injuries while defending them, he journeyed to the Other World for recovery. While he was away, the heroes utilized their powers to significantly advance society. Eager to reunite with their beloved master, they sent him detailed accounts of their accomplishments. Upon reading these letters, Eisen decided to visit each hero as he traveled across the country for leisurely sightseeing.