Mermaid scale

A is said to cure any sickness, should you go to sleep with it. Sōta's grandfather offered it to him when he was acting very quit during dinner, but it is given to Buyo to play with.

Trivia

 * This situation of Sōta receiving the mermaid scale from his grandfather before immediately giving it to Buyo to play with is similar to when Kagome receives the mummified kappa hand for her early 15th birthday in the first episode.