A visual novel game written by Kinoko Nasu.
It was a story about a youth who had Mystic Eyes of Death Perception just like Ryougi’s.
It shared many similarities with Kara no Kyoukai, and the two were also subtly connected.
It was published as a doujin work, and is currently out of print. The remake seemed to be in the works, or maybe not…?

Garden of sinners Pamphlet: Kara no Kyoukai Settings Glossary