The Kyoma Demon is a strange demon resembling a green robed skeleton who lives inside certain large mirrors found in the Inner Quarters. Most of the many mirrors in that area will reflect the player's image as they walk by; however, there are a few where the image of the Kyoma Demon will be reflected instead.
If the demon's reflection is held onscreen long enough, it will actually lean out of the mirror's surface and slash with a sword. This is also the only time when this enemy is vulnerable, so step out of the way and counterattack. Keep luring him out as many times as necessary until the foe is finally defeated, gaining with this a chance to obtain his soul.
Gaining dominance over the Kyoma Demon's soul grants Soma the Mirror World ability, which allows him to summon his very own mirror that will provide him with temporary invincibility.