Tsuurabu

Tsuurabu is a portable communication device  in the shape of flying saucer, something between a hand-held, portable, two-way radio transceiver, like walkie-talkie, and a pager. It has a display, an antenna and three buttons. Its functions are receive and send voice and text messages.

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 scenes
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.

Appearance
Gokinjo Monogatari

Anime
 * "My Childhood Friend " (First appearance)
 * "Flea Market!" (First introduced as Tsuurabu)