double suicide by mutual consent
Refers to a suicide pact where both parties agree to die together, often in a romantic context. The term emphasizes the mutual agreement aspect.
They chose a double suicide by mutual consent.
心中 is a broader term for double suicide or lovers' suicide, not necessarily emphasizing mutual consent. 合意情死 explicitly highlights the agreement between the parties.
Compound of 合意 (ごうい, 'mutual agreement') and 情死 (じょうし, 'love suicide'). The exact historical derivation is uncertain, but the term is conventionally associated with the concept of a consensual double suicide.