-( Story related, cannot be missed )-
Once you've purified the river of the Tsuta Ruins, you will see that you need to enter the giant Dogu statue to proceed further in. Inside you'll find a flower blossom floating on its own and several cursed patches. This is a shrine to one of the Hanagami, Tsutagami. Repopulate the shrine by purifying the grass three times and awaken the last of the Hanagami Triumvirate.