WoMon:Recognition

The bond of Recognition is psychic to some extent, but far stronger than a Bonding. Those who have experienced it describe it as their souls being connected, as if the other somehow makes them complete. So far no study has determined how deep the effect goes, through it is quite strong. Psychics have been able to pick up on the link between two who share Recognition quite easily. When this occurs, it usually happens that the Tamer is forced to retire.

"Eyes are the windows to the soul" they say, plus the Ar-Tits breed is known to be able to see someone's true self through looking them in the eyes. I concluded that when you look into someone, both souls touch even if very lightly and very briefly. When the match is 100% however, the two pieces stick. Permanently.