i think the reason why it doesn't really come off as creepy is because ian really has no ulterior motive and just loves him to love him. He's been up front about his feelings yet gives Eunsan the choice to accept them or not. Also, any time that he realizes that Eunsan might be experiencing discomfort, he backs off immediately. He's willing to sacrifice his own attachment to Eunsan to make sure that he feels safe and that he has his own choice in the matter.

ngl there's a very thin line of making this very cute with how he yearns for years vs him being obsessed and creepy for years. i personally like it tho