This series is more inclusive of all rivers. Although it is a story that takes place on a continent, there will be connections between the volumes. The historical background and style of each volume will change according to the author's mood. Basically, each volume is independent, so don't worry about it being a pit, because even if it is a pit, it will never be a big pit. Of course, I will try my best not to dig even small pits... Can this be considered an introduction to the work?