I didn't think about that. But if that were the case wouldn't it have taken affect a lot sooner since - if I am remembering correctly - Lucaon used to bite Kyon to get energy? If it were true, Kyon would be very upset. I honestly don't think Kyon is to blame unless he was somehow being controlled. Another thing, didn't Ryan kiss Kyon to make Lucaon jealous? Or am I not recalling correctly as I haven't re-read the earlier chapters in a while. My thoughts of when Lucaon got the VS solution is when Rain gave them that tea and the meal before the tea, which Kyon did not make himself. What do you think? :)
If it is true, I am a bit confused as to why it would have to be a kiss when it seems like for the VS solution to take effect they have to digest it. I was thinking about that as well on if that could be the reason of why Ryan isn't feeling very well right now. My main question is, how long of a process is it for the VS solution to take effect from when they drink it to the moment they turn into a Zero? Does it depend on the person?
Overall, I am hoping Kyon isn't behind this. Except if he is than he might find the cure for Lucaon.

kyon himself is the VS solution?
Lucaon started kissing him just only recently, right? Maybe that's when he got the VS solution in his system.