Dacryphilia is a paraphilia in which the 'dacryphiliac' experiences sexual arousal from watching other people cry.
Sometimes viewed as part of the BDSM spectrum, it could be considered a form of sadism. More specifically if the turn on involves trying to elicit tears from another, perhaps through pain or humiliation.
It can be a little jarring to imagine someone getting off on viewing a persons emotional distress. So try and remember that there are people on the other side of the spectrum who are aroused by being humiliated or enduring physical pain. For sure there is a person out there who is specifically aroused by themselves being brought to tears.
Therefore if the two are to meet, it's actually a beautiful love story and a great lesson for us all in sexual compatibility.