Bagrin is a character from the Kumarba franchise, originating as part of the Kumarba Channel children's project created by the company Akatsuki. His fundamental nature is that of a computer virus that has gained a personality, effectively making him a demon born from the internet. He is characterized as a mischievous prankster who despises happiness, with his official tagline being that he hates happiness and possesses a pitch-black heart.

In terms of appearance, Bagrin is a black-colored entity with demonic horns, red eyes, and a red cape. He wields a staff topped with a purple, broken heart. The character has gone through visual iterations, existing in three distinct forms. His first form is a pixelated, blocky creature. His second form is a two-dimensional illustration. His third form is a three-dimensional animation, similar in style to the show's protagonist, Kumarba.

Bagrin's primary motivation stems from jealousy towards Kumarba, a popular bear character, and he frequently plays tricks on him. He is known to appear when people are filled with negative energy. His role in the story is that of an antagonist who disrupts the peace of the internet world. In the third season, specifically episode six, he invades the land of the Oni and claims it as his own domain. He is also capable of controlling mischievous monsters that are created from negative emotional energy, using them to cause chaos.

A key relationship for Bagrin is with the character Tabris, a knowledgeable squirrel-shaped tablet device. Despite his antagonistic nature, Bagrin is interested in Tabris, who is one of the few characters that shows understanding towards him. This connection begins to change his heart, suggesting a capacity for development beyond his role as a simple villain. Another notable ability is his evolution across different media formats, transitioning from a pixelated virus to a fully realized 3D character.