Three-Legged Crow

The three-legged crow (Yatagarasu) is mentioned in various forms throughout the game.

Satan mentions in Lesson 30-1 that it is believed that demons derive their power from the three-legged crow, and have since ancient times.

There is also a three-legged crow sculpture at the entrance to the Devildom royal tomb, where demon royalty are laid to rest.

Three-Legged Crow Conglomerate (Yatagarasu)
The Devildom's biggest holding company. They are the developers of the D.D.D. (Diavolo's Devildom Device).

D.D.D.
Also known as Diavolo's Devildom Device, the D.D.D. was created by the Three-Legged Crow Conglomerate. This device is given to MC at the start of the game and functions in a similar manner to cell phones of the Human World.

The D.D.D. includes its own messaging app with custom stickers. There are three mascots that are included in the stickers: Red Devil (left), Blacjak (middle), and Nancy (right). Blacjak portrays the three-legged crow and is super popular.

Trivia

 * In Japanese mythology, the three-legged crow is a mark of rebirth and rejuvenation. Historically, it has cleaned up after great battles and symbolizes the renaissance after such tragedy.
 * The word Yatagarasu has been translated as "eight-span crow" (giant crow) and deemed to mean Supreme/Perfect Divine Crow (the number "eight" in Japanese numerology means "many", "a multitude", "perfect" or "supreme") or just "large crow."
 * As a crow-god, it's a symbol specifically of guidance.