Makikomare Shoukan!? Soshite Watashi wa "Kami" deshita??

Takumi Saiki has retired from work and is living a life free from care, when he finds he's been summoned to another world. He is one of four people brought as heroes through a secret ceremony and tasked with defeating an invading army of the Demon Lord. There's a "Hero," a "Sage," a "Priestess"...and Takumi's...a "God?" This heartwarming (?) story is about a FORMER old man that becomes "God" in another world.

(Source: AlphaPolis)