Nene's neighbor and childhood friend. He's meticulous about making every show the best it can be, making use of his flair for technology and inventiveness. He even builds robots to use on stage. His somewhat unique way of thinking often gets him labeled as a weirdo.

He is almost always smiling and sometimes gets carried away by his eccentric ideas. This includes using people as test dummies for his ideas and waterboarding them in swimming pools, as stated by Nene. Despite the apparent riskiness of his ideas, Rui does his best to take safety into consideration.  Rui also has levels of curiosity that borderline on obsession, as he loves to take toys and home appliances apart to see how they work. He is also a teasing and playful person, with an example being his constant ideas for performances that often involve putting Tsukasa's life in danger.

Please note: The x in Wonderlands x Showtime is silent! Please read it as "Wonderlands Showtime"!