Isekai Shoukan-sareta ga Kyousei Soukan-sareta Ore wa Shikatanaku Yaseru Koto ni Shita.
異世界召喚されたが強制送還された俺は仕方なくやせることにした。
A 32-year-old overweight reclusive man is struck by a bus and summoned to another world. Due to a weight restriction, the summoning system malfunctions and sends him back. A princess from that world unintentionally returns with him. To send her back, he must reduce his weight.