@historia kinda feel bad for Fan Xiao. I know he is a red flag, it's obvious. But I see the little lonely boy as well. After the break up with You Shu Lang, he constantly asked him if he doesn't want him anymore. He desperately wants someone to love him, even though he is going all wrong about it. He is clearly obsessed with YSL. Yes, Fan Xiao had never been in a romantic relationship or had any sexual relations with anyone before. Shulang is his first and only. That's why Shulang told him "I'll teach you", it's because Fan Xiao was inexperienced in the ways of pleasure and love-making.
"for where there is kindness there is goodness and where are is goodness there is magic"