Queen Rosa is an enormous rose that Ren Tsuruga gave Kyoko Mogami at exactly 12:00 p.m on December 25, Kyoko's seventeenth birthday. Kyoko treasures the rose and even bought a large vase for it to fit in. It was later revealed that Ren put a water-dropped gem into the rose, which he named Princess Rosa so Kyoko could accept his gift for her.
Ren made up a legend so that Kyoko wouldn't be able to refuse his gift for her birthday, something that Yashiro and Kanae predicts.
The rose where Princess Rosa "came out" from is named "Queen Rosa", which originated from England. The legend is about an English royal family ages ago. There was a queen who was beautiful as the big, enormous rose so she was called Queen Rosa. The queen had a young daughter, who looked beautiful as the queen.
The princess was loved by everyone so she was called "Princess of Rosa". Then one day, the princess got into an accident and died by a spring. The queen cried every day at the place where the princess passed away and until she herself died. Not long after, in the same spot, a single rose bloomed.
In the center of the large-blooming rose, there was a little girl who just looked like the princess.