beta
Idol x Fan GL?
https://www.mangago.me/read-manga/twin_cake/
Sort of fits, fan becomes the idol's manager
https://www.mangago.me/read-manga/mietemasu_yo_aizawa_san/
This one also kind of fits
So her brother who took her in(?) and gave her everything she wanted suddenly lost his memories and didn't remember having a little sister and the girl ran away and bad stuff happened to her after she got caught by someone else i don't remember. But after going back to the past she wanted to change her fate and took over her brothers duty and protect him while he doesn't remember anything.
I bet some of these ppl who are complaining here literally read BLs where the uke gets by the seme and proceed to praise the plot