I was wondering if it was possible for a vastayan to live in a human civilization in relative peace? And if so how would the reactions be to that vastayan creature living in their society?
Rengar seems to travel a lot in search of new hunts.
Rakan has been visiting a lot of human villages and entertained them in taverns or at festivals and Xayah attended one of those festivals. It seems like Ionians don't mind Vastayah living in their villages, and in cases like Rakan even welcome it.
is a big example of this actually! Iirc, he was sort of shunned by the rest of the Shimon due to his mischievous behavior, but he's found harmony under the training of Master Yi as the last student to learn the art of Wuju.
actually left his tribe after killing his father and now wanders around searching for 
and hunting other wild beasts.
left the Lhotlan tribe because...he wanted to party? Basically he left to be a performer for all of Ionia.
And lastly, 
's story does mention a lot of Vastaya being sighted in a market in Ionia alongside humans.
Assuming the magic in the area can meet the habitable standards over their long lives then I'm sure some Vastaya would be more than willing. Without magic or an insufficient amount of it, then it would be different story. But ultimately it would just be down to the preference of the individual Vastaya.
