It is pretty hard to work with a client who wants to be a slave. To have no agency in one's own life in order to gain experience... That just sounds crazy. And Kon definitely doesn't know how to handle Mari.
Kon seems to be rather insecure in her ideals about love. Because she's experienced so much, surely she couldn't be rivaled, right? She's happy that people find love because of her. But to have someone seemingly disregard her skills and having success just because of head knowledge really does make her mad!
The poor President has to watch these two employees feud because Pon knows he won't be acknowledged if he's not antagonistic. Pon just wants the girl he likes to notice him! And if having her tsun is the way to do it, so be it!
It's interesting that Pon used to be a thin guy before. I wonder how he managed to bulk up?