People are really surprised by this, now, after 37 chapters ?
I mean, it was kinda obvious Eugene loved Hari since the 1st chapter, before she was sent to the past.
Remember, he didn't even wanted to go to her marriage (because he love her, and can't really send her to another man) and she had to wait for years before she got his approval (He love her, but at the same time couldn't be with her).
Hari in the current life was only with Eugene for something like 1 year, the next 6 years were with her ex-fiancee family, he is already more of a brother figure than Eugene ever was.