I have no clue where everything is getting this "spoiler" from but the hate comments annoys me as well. If you don't like the story fine, no need to hate on it and the way the author writes it. #－.－)
you can check the comments again since its everywhere but:
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so the spoilers say that arien will become some cool magician and take all of the familiar's attention and go on adventures and whatever, and arien will hardly ever appear again and will be tossed aside to a side character, no more twin dynamics. he'll be some sort of weak swordsman while she has all the fun and love basically
i dont know why the hate comments but the story is not that bad, I mean kinda annoying because of the naiveness of the mc but its still good. and what is this spoilers everybody is talking about? i knida feel left out.