弄ぶ

1. Origins, structure, and basic meaning

• Structure: 弄ぶ (もてあそぶ) is a transitive verb meaning to fiddle with an object or to toy irresponsibly with someone's feelings.
• Basic usage: 鍵を弄ぶ describes idle handling, while 感情を弄ぶ describes treating another person's emotions without sincerity.
  • 彼は退屈そうに鍵を指先で弄んでいた。 — He idly fiddled with the key between his fingers.
  • 人の感情を弄ぶような行為は許せない。 — Toying with another person's feelings is unacceptable.

2. Common pitfalls and similar expressions

• Object and emotion
  • With a physical object it means to fiddle with it; with a person or feelings it has the strongly negative sense of treating them as a plaything.