Sol

"Delgoran was a friend of mine, until he suddenly changed and kill my father."

- Sol upon describing Delgoran.

Sol (ソル, Soru) is an boy from unknown alien species that appeared in Ultraman Cosmos episode 42.

Ultraman Cosmos
Sol and his father, who is a biologist, traveled the galaxy with their monster friend, Delgoran, but however, the monster was affected by Chaos Header, turning him into Chaos Delgoran, kills his father and damaging their spaceship, causing Sol to be stranded on the asteroid.

One day, he communicates with an human teenager named Shunji Horimura throughout his computer, as they become fast friends. However, with Chaos Delgoran approaching the Earth, he seeks Musashi's help to stop the monster as he becomes Cosmos and purifying Delgoran. Sol thanked Musashi and bids farewell to Shunji and reveal his true face (he previously wore a robe to hide his identity) as the asteroid that Sol resides begins to move from the orbit, cutting of their communications. Shunji decides to become an astronaut, vowing to meet his alien friend someday.

Trivia

 * Sol was voiced by Mami Matsui.
 * In the Tsuburaya All Monster photobook, he was credited as space boy (宇宙少年, Uchū shōnen).