Toudou Haruhiko is a 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 Stalion. 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 she can re-cast the summoning to open a portal - but that is conditioned on Haruhiko losing some weight.