異世界帰りの大賢者様はそれでもこっそり暮らしているつもりです (Associated Names)

After being transported to another world at age 15, Saitou became a great sage, defeated the demon lord, and safely returned to Japan. Expecting to live a humble life in his hometown, he instead discovered that 19 years had passed. Not to mention after saving his beautiful former classmate and helping yokai, he finds himself…