Age: 16 Height: 149 cm (4' 10") Birthday: January 8 Ruka Suirenji is a dance idol and a doujinshi creator. She is a friend of Chiharu. Ruka is talented at drawing, having drawn the doujinshi Nagi and Chiharu were selling at the doujinshi convention under the pen name, Fly Dolphin. She is also a popular idol, being able to sing and dance at the same time, and has many fans. Ruka has a determined and hardworking personality, shown when she insisted on returning for work despite her injuries, and when she told Chiharu that she would take care of her own bad luck.
According to Chiharu, Ruka has a similar past to Hayate, having been abandoned with a large amount of debt, namely, 150,281,000 yen. She aspires to be a professional mangaka. Ruka's pen name, Fly Dolphin, was originally the name of the performance office her parents used to own.
In chapter 382 of the manga she realizes that she is in love with Hayate and kisses him. In 383 she confesses to Hayate. She ends up being rejected by him, because he is working as a butler for Nagi, thus Ruka challenges Nagi who will sell more copies of their doujinshi. A sum the height of Hayate's dept will be the prize.