Welcome To The Isekai Hotel! summary:

Richii's parents died in an accident when he was in junior high school, leaving him alone with his doting sister Towa. Three years later, his sister also disappears, and even Riichi is summoned to another world where he is reunited with his sister. In the other world, Towa has become the most powerful hero!This is an erotic love comedy in another world where beautiful women are always pestering our protagonist!