Can’t remember the name of this manga, I believe it was unfinished- maybe only around five chapters?

I think it’s about a group of students on a trip into the mountains and they’re staying with a family in their home. One of the boys finds a girl locked in a shack outside and thinks the family has kidnapped her and says he’ll save her, but when the rest of the group finds him, he’s dead in the shack with a doll, not a human girl.
They’re trapped there also, due to a tunnel collapse or something?

Sorry, nevermind, it was Ningyou Touge.