This is a differing retelling of the couple of weeks before Watanagashi. Pay attention to the calendar dates so you'll know when a different story is being told. I can't go in depth but just keep watching and depending on the quality of this remake you'll more or less understand what is going on.
think you haven't watched the original? You should try to watch the original as well. This "Gou" version is so far similar but should derive from the original somewhere since in the 2nd episode we already saw Rika's true face and Hanyuu... So this should be something close to a sequel to the original.