Amon, playing this game has been an incredible experience. It's taken me two playthroughs, each unlocking a different ending, your explanation of the plot, a playthrough on Youtube, and reading Gyossait's age on TvTropes.com to understand everything. Finally realizing what "One day, I'll grow flowers" really means was SO CREEPY and very intellectually rewarding. Another a-ha moment was when the dog says something like, "Her words give them new eyes" - that means Gyossait's voice mutates the humans into these vicious monsters!
A beautiful story of redemption, or a killing rampage across a ravaged world? The player decides, and that's awesome! The art was gorgeously creepy (the trees and flowers, all white and twisted), and the music really set the eerie mood. When Gyossait screams near the beginning of the game, I was scared shitless. I give you kudos for that!
The final level (deep within the Earth, before the final boss) was pretty frustrating, but beating it was rewarding.
The story is brilliant, told very subtly. I especially loved the story of Uzaza - a well-meaning individual who became twisted by the power of Gyossait's heart. It's still hard to decide if he was good or evil - his guns required people being sacrificed, but they saved people form the monsters. It's a tough verdict.
Amazing, thought-provoking game with stunning imagery. I will be playing your other games!