Does Oyaka has sadistic obsession with Nagare? Why did he said "I let him win and escape" when Nagare die. He also looks sad and regret that he can't see Nagare anymore. The happiest face Oyaka ever made is when Nagare cry in despair before jumping. The way he looks happy at Negare in Shikimi's flashback. (Everyone in the bully team look at Negare with hatred except Oyaka). Normally Oyaka looks at everyone with bored and disdain.
I definitely think he is psychopatic sadist and just like how Nagare never submit to him. Like in his brain, it is a competition to make him submit to him. Everyone around him worship him. He is best student, good looking, smart, charismatic and from prestigious family. So to see Nagare not worship or submit to him make him obsessive. I guess Negare win in his brain meaning he can't get Negare to submit to him to the very end.
I don't think he is in love with Nagare but definitely see him as his favorite experiment hobby.
I can say he definitely got that toxic bl vibe tho. That famous for some reason that I cant comprehend.