I'd like to offer Syon up for two of Joukos plots. Both the bad experiance one and possibly the mating one.
Syons extreamly prejudice against naything that isnt a cerynei, and it shows when he meets them. Usually just outright ignoring if not violence if the other soquili continues their attempts to talk to him or get near him. With the potential to lead to mating later down the line. After the whole 'bad experiance' plot, as Jouko, as you said, is a bit of a flirt I can easily see this riling Syon up, since her attentions wouldnt be placed soley on him any longer, and he's quite the possessive b*****d.
Even though he has a somewhat skewed personality he's a big softy when it comes to his mate, when/if he gets one.
To not write half a novel about his personality and such,
here's his info and such. x]