Definition: Kuon is a Japanese word that could mean eternity or nine grudges.
"The tune of Japanese Taiko Drums and the dark hymms of children are heard throughout the night. Residents wander like ghosts, and hungry demons creep in the darkness. The Heian Kyo Period of Ancient japan where mysticism and magic will require you to reach deep within your soul to uncover the mysteries of the undead."
The player can choose either the Yin or Yang phase when starting out so it don't matter if you bigin with the yin before the yang phase and vis versa.
The whole game revolves around the strange events at a Japanese manor , nearby shrine and secret underground. The Yin Phase revolves around a sheltered girl named Utsuki living at a shrine. Her father is a Civilian exorcist who has been summoned to investigate the weird events in the manor. When he does not return, she and her sister travel to the manor in search of him. At the manor, eerie hymns put her sister into a trance, and she vanishes into the gloom. Utsuki must now find both her father and her sister. The Yang Phase revolves around Sakuya, exorcist-in-training under Utsuki's father. She and her fellow students have been sent to investigate the strange happenings at the manor. along the way she will encounter Utsuki which will lead Sakuya to uncover the malevolent truth. The third phase, Kuon, is unlockable after defeating the first two phases. It's a spoiler so you shouldn't read it.
If you are reading this, its a final piece of the horror vision; you will play with the rival of Doman and the one how will stop the curse.