玉たま手て箱ばこ

noun

Urashima's casket; Pandora's box

Refers specifically to the treasure box given to Urashima Tarō in the famous Japanese folktale. When opened, it releases smoke that ages him instantly. Also used metaphorically for something that brings unexpected consequences when opened.

• 浦うら島しま太た郎ろうが玉たま手て箱ばこを開あけると、白しろい煙けむりが出でておじいさんになってしまった。

  When Urashima Tarō opened the casket, white smoke came out and he turned into an old man.

• その秘ひ密みつの書しょ類るいはまるで玉たま手て箱ばこのようで、開あけたら大たい変へんなことになった。

  Those secret documents were like Pandora's box; opening them caused a huge mess.

noun

closely guarded treasure; precious secret

Figurative use: something precious that one keeps hidden and rarely shows to others, like a cherished memory or a prized possession.

• 祖そ母ぼにとって、その古ふるい写しゃ真しんは玉たま手て箱ばこのようなものだ。

  For my grandmother, that old photograph is like a closely guarded treasure.