Calappa japonica is a large crab, and has a yellow and red colouration.

[1] The length of carapace is approximately .65 times the width, with a tuberculated surface.

It is now known to occur in regions as far away as Africa and Western Australia,[1] and lives in waters up to 250 m (820 ft) deep.

After breaking open the shell, it uses its left pincer, which is sharper and longer than the right one, and better at picking out the soft tissues.

When it is disturbed, it folds its chelae (pincers) in front of its face and retracts its walking legs, forming a compact, well-armoured box-like structure; this defensive stance makes it appear to be embarrassed, and has led to its receiving the name, "shame-faced crab".