Mikako and Tsutomu got them from Ruriko as a present on their 16th birthday and use all the time. Later, Ruriko gives tsuurabus to all members of Akindo as a celebration present for their Flea Market debut.
Behind the scenesEdit
Tsuurabus look like a toys for small children, most likely they were put in the anime for merchandising purpose. They were presented as something cool and important only in the anime.