In Tsukihime's Kohaku route, Shiki falls asleep and has a "dream" after the welcoming party.
In it, he (or SHIKI) encounters another serial killer. They drink coffee bought from a vending machine together and have a conversation. Afterwards, the other killer decides to leave the city, believing that there would be trouble if the city had two serial killers.
I'm wondering who this other person was, and if they, too, were sent by the same person who sent Nrvnqsr Chaos to kill Arcueid Brunestud. (I remember reading about it the other day, but I can't remember who; I know for sure it wasn't Roa.)