Moon is an alien of human-like appearance, born in an Alien Factory in 1984 and adopted from a UFO. With a ball-shaped or manjū-shaped head, a small nose, black oval eyes, and typically hidden ears, the character’s theme color is blue, reflected in personal items such as a smartphone, house, and ninja costume.

Moon exhibits a troublemaking personality, playing tricks on friends when dissatisfied. Traits include stubbornness, capriciousness, laziness, and a tendency to create messes. A self-proclaimed winner who often loses games, Moon displays sore loser tendencies and cheats. Interests include watching porn, using curse words, playing Just Dance, and engaging in weirdly happy behavior. Moon also stalks Jessica, meticulously documenting her hobbies and routines.

The character enjoys various foods, owns a guitar, and specializes in telling ghost stories. Moon shares a significant friendship with James, considered a best friend, and is friends with Brown. The relationship with Cony is inconsistently documented, with one source identifying them as childhood friends and another stating they were never friends. Moon is childhood friends with Cony, James, and Brown, and together they buried a time capsule containing toy spaceships.

Initially dubbed the "Cheating Leader" by friends, Moon was later renamed the "Planning Leader" for frequently assuming the planner role in the group. A notable friendship was formed with a roomba named Salusa; after initial denial, Moon supported Salusa's romantic interest in another roomba named Bobo.

Moon is part of the superhero team LINE FIVE, operating under the alias LINE Blue Moon, and is the only member capable of flight. One source notes the character’s real name as Ralph. Moon is based on Sam from "Zip Zip" and Arthur Read from "Arthur."

In the "LINE OFFLINE" series, Moon works as a salaryman at LINE Corporation, maintaining a problematic reputation and a desire to become the best office worker.