Haruhiko Toudou is an obese NEET who got summoned to a different world when he was about to get hit by a truck. Unfortunately, the summoning system malfunctioned due to exceeding the weight-limit, and he was sent back to his world with the summoner Princess Shella. He retained some Lv.1 skills, but one skill's level got corrupted into infinity, so he got a powerful version of the skill Judgement, embodied as the cute girl Infinity-chan. She tells them that Shella can return to her homeworld if he loses some weight, so that she can re-cast summoning to open a portal.

(Source: MU)