Harumade, Kururu. - Sumikko Soft
For some reason, the protagonist ended up spending his spring break with four girls in a remote area that had no wireless reception and didn’t even have a convenience store. There was only a school building that seems to be on the verge of closure, a large dormitory that looked like a hot spring hotel and a chimney that stretched up to the sky as far as the eyes could see. He thought that he would just spend some peaceful days here, but that’s when one of the girls Shizuka declared that they will make this place his harem, and started stripping in front of him in his bewilderment.