Haesu doesn't understand the concept of humans, hence he could only imitate their appearance but after all he still is a ghost inside.
Honestly, as delusional as it sounds I really hoped that both Eunha & Haesu would be happy together. Whether that's platonic or not, it doesn't matter because both of them are incredibly lonely people who was left behind.
I genuinely adore them but I don't think this manhwa will have a happy ending...