I'm confused, who does the professor actually like? Wooju or Jiheon?

neither

So what is his real goal? Is it just a trial of that drug?

I think he's insane and like insane that do insane things

Oh right, I get it that could definitely happen, since he’s crazy

the authors kind of hinting they might be siblings so idk hes definitely plotting something to jiheon

Right ,I was confused at first, I thought the professor liked one of them, but that wasn’t the reason after all

None. For me I'm thinking he's plotting some type of revenge or just hates Jiheon and wants to destroy him. He's definitely not into Wooju but Jiheon is and Wooju also likes Jiheon so he's trying the best he can to break them apart