Question: what is the square thing on the back of a kimono?
Answer: An obi (Japanese: 帯) is a sash for traditional Japanese dress, keikogi (uniforms for Japanese martial arts), and part of kimono outfits. The obi for men's kimono is rather narrow, 10 centimetres (3.9 in) wide at most, but a woman's formal obi can be 30 centimetres (12 in) wide and more than 4 metres (13 ft) long.