Kin-Ki (金鬼) whose name means "Gold Oni" is one of the four oni controlled by Fujiwara No Chikata (藤原千方) during the mid-Heian period of Japan. Kin-Ki's body is so strong that no physical weapons in existence can pierce it.
"One of the four oni Chikata Fukiwara was said to have controlled during the Heian period of Japan. His body was so tough, swords and arrows bounced off of him."
—Shin Megami Tensei III: Nocturne compendium
Kin-ki is one of four optional bosses that can be fought in the Ikebukuro Tunnels. During the fight, he will regularly cast Beast's Eye, followed by a buff or debuff, and ending with a physical attack, such as Blight or Hell Thrust. Once his health reaches a low enough point, he will switch to Dragon's Eye. For this battle, it is recommended to bring demons with Dekaja and Dekunda to counteract his strategy.
Shin Megami Tensei IMAGINE[]
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.
Shin Megami Tensei IV[]
Kin-Ki is the sub-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.
Kin-ki later appears as a normal enemy in Infernal Tokyo.
Shin Megami Tensei IV Apocalypse[]
Kin-Ki can teach Nanashi the Power Punch, Mortal Jihad and Charge skills through his Demon Whisper. He benefits from learning Physical, Electricity and support skills.
Shin Megami Tensei V[]
"One of the four oni controlled by Fujiwara no Chikata, its body is so hard that no weapons can penetrate it. It and its comrades fell into hell through holes that can still be found in Mie Prefecture, Japan (the modern-day Iga Province)."
—Shin Megami Tensei V lore
Persona 4[]
"One of the four oni controlled by Fujiwara no Chikata, its body is so hard that no weapons could penetrate it."
Kin-Ki's Dodge Psy skill can be used in a fusion recipe to further the StrengthConfidant with Caroline and Justine. After leveling Kin-Ki to level 27 so he learns Dodge Psy, the protagonist can fuse him with Sui-Ki to produce the desired Ame-no-Uzume that knows the Dodge Psy skill.
Taizo Naguri's Shadow takes the form of Kin-Ki during the request, "Who's Been Assaulting People?", which his name can be accessed if the protagonist works at Rafflesia. When defeated, he will drop the Charge skill card.
"One of the four oni controlled by Fujiwara no Chikata, its body is so hard that no weapons can penetrate it. It and its comrades fell into hell through holes that can still be found in modern Iga."
—Persona 5 Royal background
Kin-Ki's title as a Shadow is now "Samurai Killer". Kin-Ki is no longer weak to Psychokinesis Skills and can now repel Gun attacks instead of simply resisting them. When itemized through Electric Chair execution, Kin-Ki will now yield a Varja Blast Skill Card. During a fusion alarm, Kin-Ki will yield a Vicious Strike Skill Card instead.
Requests Macca. After using on the same clan of demons thrice, any demon of that clan will take away one third of player's Macca forcefully in the next encounter.
Kazuma Kaneko did not intend Kin-Ki to use any weapon, unlike his fellows. But likely for saving an individual set of skeletal animations, his 3D model is given the same club of Oni and uses the same attack animation. This design decision continues to Persona 5, when all 3D models and animations were given a revamp. In Persona 5 Royal his club is removed and given a new set of animations, which was retained for his future appearances in games with 3D models.