"An humanlike spirit of Murngin lore that lives in the jungle and moves at night. He is the reincarnation of the "shadow soul" of humans, and kidnaps and eats children, sometimes causing war with humans."
—Shin Megami Tensei IV Apocalypse compendium
Mokoi appears in Shinjuku at the south entrance and the west entrance passage, as well as the northern areas of the Fairy Forest, past the central gate. He can teach the Zionga, Head Crush, Dream Fist and Mazio skills during Demon Whisper. Mokoi has an affinity for Physical, Electric, and ailment skills.
Devil Summoner: Soul Hackers
"An evil spirit of Murngin mythology, believed to be reborn shadows. They kidnap and eat children, and strike down sorcerers who use black magic."
—Devil Summoner: Soul Hackers Compendium
Devil Summoner: Raidou Kuzunoha vs. The Soulless Army
"A human-like spirit of Murngin mythology that lives in the jungle. A Mokoi appears to strike down those who use black magic."
—Devil Summoner: Raidou Kuzunoha vs. The Soulless Army Devil Chart
Persona 4
"An evil spirit of Murngin mythology, believed to be reborn shadows. They kidnap and eat children, and strike down sorcerers who use black magic."
—Persona 4 Compendium
Mokoi can be obtained through Shuffle Time in the Steamy Bathhouse. After fulfilling Quest 43, the protagonist will be rewarded with a Mokoi Doll that he can place in the shelf in his room.
DemiKids Light & Dark
"A greedy earth demon that preys on the spirit of those with many years ahead of them."
"A humanlike spirit of Murngin lore that lives in the jungle and moves at night. He is the reincarnation of the "shadow soul" of humans, and kidnaps and eats children, sometimes causing war with humans."
My name`s Mokoi. A Jaki. I have tons of lady fans. You know, right?
...Guess it's time for a vacation. I hear Istanbul's nice this time of year.
Gallery
Artwork from Devil Children Red/Black Book
Mokoi as he appears in Devil Survivor 2
Mokoi as he appears in Raidou Kuzunoha vs. The Lone Marebito
Mokoi as it appears in Card Summoner
Trivia
Although it is, like any demon, optional to recruit or keep in the actual games, a Mokoi seems to make up a very important part of Raidou Kuzunoha the XIV's "canonical" demon team. In every single appearance Raidou has made outside of his own games where he summons demons (that is, Devil Summoner: Soul Hackers, The Lone Marebito & the "Chronicles" edition of Shin Megami Tensei III: Nocturne), the Mokoi has made a major appearance. It is so important in Chronicles, in fact, that it opens the cutscene before the fight between Raidou and the Hito-Shura, in addition to being one of Raidou's major attacks.
This Mokoi is often seen using abilities that are all but impossible for a playable Mokoi to possess, such as a powerful boomerang attack. It also has impressive (to say the least) stats when targetable in Soul Hackers.
The only other demon to feature so consistently on Raidou's team is Moh Shuvuu.