Soul tie

A soul tie is defined as a spiritual/emotional connection people have with someone after being intimate with them, usually from engaging in sexual intercourse.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Empath and Smurfette felt such a connection with each other after their first kiss at the penultimate chapter of the novel, which Papa Smurf saw as a prophecy that they would become soulmates, which was fulfilled ten years later in their marriage.

Tapper, being a Christian, warns his fellow Smurfs about the possible danger of developing a soul tie with somebody they may have intercourse with, and exhorts them to stay pure until marriage.