I think Ryan's abilities have something to do with reading memories/predicting the fututer/bending time, which would explain how he knew about Kyon's visit to Sihan beforehand.
When Ryan explained to Kyon about the black knife Lucaon gave him, he used it to slash a cup in half, but then he put it back and the cup became back to normal, so maybe he can mess with time somehow. And when Lucaon started to turn into a zero, Ryan used his abilities to reverse the process and stop the zerofication, but he himself also said that he could only stop the change if it was cause by intense heartbreak, if it was the VS solution then he'd be powerless, suggesting that he can alter time/memories.
In chapter 34, the servant who hit Kyon also said erasing Kyon's memories is important because Lucaon has ties with other royals, one of them can read memories. I think the royal mentioned here is Ryan.
how come ryan knows about kyon visiting sihan before it occur 10 years beforehand? he asked sihan to be nice to him ?!