This is the story of a man known only as Gen, who used to be an assassin. Nobody knows his past, his real name or his age, only that he is now working at Tsubakiya, a secluded onsen inn. He had put down his weapons and intended to lead a quiet, peaceful life, but it seems his past is not willing to let him go so easily. The onsen inn gets guests from all walks of life, and anything can happen. Some guests come to end their life. Some guests just want to get away from everyday life and go crazy. There are TV shows and incognito celebrities. Every guest staying at Tsubakiya has their own story, just waiting to unfold.