ransom demand
Refers to the act of demanding a ransom, typically in kidnapping or hostage situations. Often used in news reports.
The criminal made a ransom demand.
A ransom demand call came in.
The kidnapper made a ransom demand.
The police did not comply with the ransom demand.
The family refused the ransom demand.
A ransom demand arrived in connection with the kidnapping case.
身代金要求 refers to the act of demanding a ransom, while 身代金 refers only to the ransom money itself.
Compound of 身代金 (ransom) + 要求 (demand). The exact historical derivation is uncertain, but the components are transparent.