I would feel less troubled about this if Eugene had a less...dark? cast to his affections. Like I understand he is struggling to fight back his emotion but the way he frames his emotions seems to border on obsessive and possessive, which makes me worried...
I feel like I would feel better about this if Eugene and Hari had dated more. I know it isn't really in character, but if they are both each other's first loves...idk, it just hits different as opposed to if they had maybe dated someone else beforehand. I'm almost certain that they will end up getting together (the prince being set up to having a mad crush on Eugene's fiance is too convenient to be anything else but a setup for Eugene and Hari to end up together) and it just...really feels odd that your adopted sibling is your first love.