"Rappa Renshūchū" (ラッパ練習中) is the 4th single by Mayu Watanabe, released in Japan on July 10, 2013.
An illustration contest was held on the website pixiv for the Complete Limited Edition.
It features the "Rogoku Yuenchi kara Mayuyu wo Sukue!!!
in Tokyo Dome City Attractions".
The other editions were done in collaboration with Oreskaband and was directed by Fantasista Utamaro.