Backpacks that kids use in elementary schools in Japan. They are incredidly expensive because they are supposed to last throughout the entire 6 years of elementary schooling. They are made out of leather or synthetic leather-like materials. New leather randoseru can cost 30,000 yen or higher, but if they are made from the synthetic material clarino, the price is lowered.
The traditional colors are red for girls, and black for boys. Randoseru are in demand by anime and manga fans, but few manufacturers produce them outside of Japan.