That and her character as a whole is pond scum at best. The whole worshipping the ground Karen walks on like she's the second coming of Jesus, putting her on a pedestal with her own vision and ideals of her, her trying to make and keep Karen as she envisions her to be. I could go on.
Honestly, story didn't need her or this lame involvement of hers. Easily could have gone the same route without this "A RomCom has to have this character" addition.
It does no favors to Karen, either. She's already strained and stretched to the limit trying to uphold an image of herself for the sake of her father's opinion of her--like how she works so hard to be the best at everything because she wants to take over her family's business, and she
actually has to work to do so because she's not some naturally gifted genius.
For Tsumugi to come in and, entirely unilaterally, force her own ideals on Karen and try to separate her and Kageyama like this is already bad. But she's now exploiting Asahi's love for Kageyama and her vulnerable position in the wake of that crash out to push Tsumugi's agenda along.
None of what's happening is because the
people being affected want it to happen. And I kind of consider that subpar writing.
Maybe there's a reason the author's gone this route, but I worry that it's because they couldn't work out how to make Kageyama care about Asahi enough to chase after her, after what he said to her last chapter. So while I'll stick through to the end, I'm just a bit concerned--because if the end game
is Asahi winning, it'll take some doing to sell me on this being the way it should have happened.