Sumeba Miyako no Cosmos-sou (3) Haikaburi-Hime ga Dokkoi

is the third volume of the Dokkoida?! light novel series, written by Taro Achi and Illustrated by Sumi Miya. It was released under the Dengeki Bunko Imprint in February 2000.

Synopsis
Hi, hello. This is Suzuo Sakurasaki. While attending a vocational school aiming to be a childcare worker, while still being laughed at by the world, he is also a transformation hero of justice called Dokkoida. This time, Kosuzu, who is not her true sister but is supposed to be her sister, will play the role of Cinderella at the arts and sciences. I had everyone at Cosmos-sou help me to practice the child bell, but Tatsuya, who played the role of the prince on the day of the arts and sciences, suffered from acute appendicitis. It's a little forcible, but he's the only one who can save this pinch !! But this time it's a child size?

(source: Bookwalker JP - Translated)