Singsongalong(sp?) Kingriver would be a fantastic villain in Baba's other series, Ride-on King. At least it shows he can write much more realized characters, who pursue their interests with far more complex motivations and angles than "I want to win at bloodsport for muh nakama." Instead of some middle class brat treating martial sports as some monumentally important activity, to Singhsak it's just one way of making money among others. He's easily the best character, as far as I'm concerned.