闇取引

1. Origins, structure, and basic meaning

• Structure: 闇取引 is read as やみとりひき and is a noun for an illicit transaction conducted secretly to evade law or official regulation.
• Basic usage: Use 闇取引に関わる for involvement and 闇取引で売られる for sale through that illicit channel.

2. Common pitfalls and similar expressions

• Secret is not enough
  • The word implies illegality or evasion, such as trade in stolen goods, rather than any transaction kept private.
• Roles of the particles
  • に marks the matter someone is involved in, while で marks the illicit transaction as the means or channel of sale.