I'm the Villainess, So I'm Taming the Final Boss isn't based off of a shojo manga, but it is based on a light novel which is directed towards the same demographic – a young female audience. It also follows the same popular shojo conventions and tropes – with enthusiasm. It is an isekai, but it doesn't try to hide the fact that it's all about the romance.
Source:https://www.cbr.com/im-the-villainess-so-im-taming-the-final-boss-shojo-cliches/