Kin-Ki can only be obtained through fusion. He appears as a field boss on Shinjuku field when summoned by one of the charms the Yaksini NPC in Ichigaya Camp's B11 will trade for magnetite. A strengthened variant called Peerless Steel-Bodied Kin-Ki can be fused by players after completing a series of G1 Trial quests from a Cathedral of Shadows researcher in Ikebukuro. This variant learns the unique skill Lightning Flash Massacre.
Kin-ki is the boss faced at the end of the Challenge Quest, I Want to Make the City Bright. He has created a Domain over a relic spot in Ueno - Central Way and must be defeated to obtain the LED Lightbulb. He can be refought for the item he has after a certain amount of time has passed.