Osananajimi no Watashi wa Mob de Itai Noni, Naze ka Heroine no Renai Taishou ni Natteiru.

Histoire

When Mashiro Yukizuki is reincarnated into the world of a gal-game as “Ryona Amezuki,” one of the heroines of the game, she decides she wants to live as inconspicuously as possible. But when she helps to rescue “Ririnri Hinahoshi” from being harassed by a man downtown, she finds herself in the middle of a love affair. Now everything she tries backfires, as Ryona finds herself attracting the love interest of more and more heroines…

Synopsis via AniList (en anglais).