No, he's not a yandere. He doesn't even like Jaerim. It's all for that girl he's in love with. You'll see where this is going next chapter.
That's not it. A yandere is someone who is willing to go to violent acts for the one they love. He may not love Jaerim, but he's ready to use violence towards him in order to secure the one he loves. So he IS a yandere.
Yeah, he is doing it because of love wherever he loves him or not.
And pls, don't tell me what is going to happen next chapter! I haven't seen it yet :P
Could it be? Is he Yandere?