• English / United States: Soleil
• Japanese / Japan: ハルヒ
• Japanese (Romanized) / Japan: Haruhi
• Japanese (TL) / Japan: Haruhi

Soleil is the mistress of the Eclipse Castle in the Johto Region. In order to be recognized as the castle's owner, it was necessary for her to safely hold the Eclipse Festival that is held on the day of a total solar eclipse, which happened to be the day Chloe Cerise visited. Both Soleil and Chloe look so similar that they decided to swap clothes to fool their friends and family. Not only are their faces similar, but their Japanese names are based on times of the year as haruhi (春日) means a spring day while koharu (小春) means little spring, and refers to late spring or late summer. Soleil felt like it was fate that brought the two of them together that day.

Ilunas ends up kidnapping Chloe, thinking that she was Soleil and demanded that he be named the new lord of the Eclipse Castle. His plan failed when he didn't realize that Chloe and Soleil looked alike, so he outright attacked her during the Eclipse Festival ceremony.

After Ilunas tries to fight Soleil and ends up losing, she still decides to allow him to become her friend and help her as the mistress of the Eclipse Castle as she and Helia had been waiting for their missing 'moon' to finally return to support each other.