Tiara is Pride's younger sister and the original protagonist of the game. Events from the game are mentioned throughout the series, with Tiara being presented, like a physical, living hug plushie or holding hands while the male protagonists—aka the romance candidates of the original game—talk about Pride (in a negative and hateful way). To make it clear, even in the original game, the story is just about Pride, while Tiara only serves as a support character for the princes, filling the role of a protagonist and lover rather than an active protagonist. However, after Pride gets reincarnated into the game's world and becomes the protagonist, it is no surprise that Tiara's impact in the series is reduced to that of a cute little sister with her head in the clouds, loving to read fairy tales while everyone else is working on getting better to support Pride—including Pride herself—for the goal of making the kingdom a better place for everyone. In a way, if you removed her from the anime, you wouldn't notice any major difference, though some cute scenes won't happen.