Jun Hiiragi is the main character debuted in the Kuru Kuru Shuffle pilot. He is Keiichi's younger brother who used to live in London at a school of Japanese students but comes back a few years later, just in time for Kuru Kuru Shuffle. He is a ninth grader in Yumegaoka Junior High School and is the same grade as Uta, Miki, Mana, and Kakeru. He replaces his brother as Kuromi's source for the Dark Power, giving recharges with his guitar. Jun has a crush on Uta, but is rejected several times because she doesn't take him seriously; mostly because he is always making jokes and puns. He is good friends with Kakeru Kogure.
In the past, Jun is always been overshadowed by his brother, Keiichi, thus he has an intense hatred for him, which is the reason why Dar-chan took his consciousness, and Keiichi was indifferent to him. He always taunt his brother and even wanted him to say "uncle", which angers Keiichi. He has a sad past despite living in a wealthy family. Jun isn't very active or energetic; because his power of concentration runs out after five minutes, but later it is eight minutes. Other than that, he is kind-hearted, cheerful, and fun-loving. He loves making jokes, which sometimes annoys his friends. All he longs for is to be loved by his family. At the end of Kuru Kuru Shuffle, he and Keiichi apologize to each other and rekindle their relationship.
Jun has messy chin-length dark magenta hair with gray streaks on the right and gray eyes. In later episodes, it was revealed that his hair used to be gray, like his brother. He usually wears a wild outfit.
Hiiragi (柊): Hiiragi stands for ''holly''.
Jun (潤): Jun stands for "favor" or "charm".
His name means, ''holly favor" or "holly charm"
- He replaced Keiichi as the source of the Melody Key.
- He is the fifth being who was possessed by Dar-chan. The others are Baku, Keiichi, Bako, and The Minister of Maryland.
- He loves jokes, along with Masahiko, Uta's father.
- His musical instrument is Electric Guitar.
- When he was possessed by Dar-chan, he wore a demon-like outfit.
- As a Bunny-Eared Ranger, he wears a Red and Black Costume. His weapon is ''Don't-make-fun-of-me Beam!''.
- He debuts in Season 2.
- His best friend is Kakeru, despite their differences. They are also rivals for Uta's affections, but they never seem to fight each other for her.