Cybelle (Japanese: シベール) is a French-singing Mars' Brightest contestant with a dangerous obsession over Tuesday.
She is very tall and has a slim figure. She has pale skin and green eyes, and her hair is short, which she puts some strands of hair behind her ears.
She dresses herself up kind of tomboyish, with a oversized turtleneck white t-shirt and a pair of trousers with suspensers. She wears a gray pair of sneakers with oversized white socks. On her left ear, she has a blue earring.
When she was trying to disguise herself not to be discovered, she wore a black hat.
During her first appearance, Cybelle seems to act very energetic and enthusiastic when meeting Tuesday, stating herself as her biggest fan and asking for multiple favors in quick succession. It's later found out that she is extremely obsessive towards Tuesday and anyone who isn't her are quickly ignored. Cybelle is generally regarded as a bit creepy in her interactions with Tuesday, and can sometimes be seen as full on crazy. She takes her love for Tuesday very seriously, and has no regard for others feelings once so ever since she quickly asks Tuesday to make a new band for her with Carole excluded from it.
Cybelle met Tuesday Simmons in the dressing room at Mars' Brightest Competition and was excited to see her. She hugged her and wanted a kiss, but was stopped by Carole Stanley. Cybelle explained she was big fan of her and Tuesday realized who she was from her followers. Cybelle was excited that they will be competing in the same competition. She then requested exchanging numbers with Tuesday and she agreed.
When Tuesday and Carole went in the dressing room, they saw Cybelle who quickly went and hugged Tuesday, ignoring Carole. Cybelle started fixing Tuesday's hair and expressed her desire to have a group with Tuesday named "Cybelle and Tuesday". Hearing this Carole took Tuesday out of the dressing room. Backstage, before her performance, Cybelle went to Tuesday, saying she was nervous and requesting a hug. As Tuesday hugged her, Cybelle bit her neck, giving "her mark" and proceeded to the stage happily.
In the first round, Cybelle was facing Angela Carpenter. When she went on the stage, she said she chose to sing in french, because it was elegant and beautiful language and that people express beauty only when they were young, so before getting old, she wanted to leave something. Cybelle then sang her "La Ballad" song.
The jury liked her singing, but decided that Angela did better and Cybelle lost to her. Cybelle quickly ran to Tuesday, seeking comfort and saying that the next time they can compete as "Cybelle and Tuesday". But Tuesday apologized, saying she can't do two groups. Cybelle couldn't believe, saying she even put her mark on her and left angry.
Cybelle was in the dressing room before round 2 started. She met Carole and Tuesday, saying that Tuesday was her only hope and solace, thinking she would have understood her. She then said her goodbyes and left.
She then returned and left a present in Tuesday's dressing room for her. As Tuesday opened it, it burned her hand. Later They realized it was Cybelle and caught her, as she was being taken away, she saw Tuesday, telling her that she was happy she got hurt, as Tuesday hurt her too.