The possession premise is an excuse to watch two people awkwardly fall in love without the guilt eating them alive. Hiyori gets to want Yuya without Mitsuki's shame getting in the way; Yuya gets to be confused and charmed by someone who looks like his sister but isn't. The show knows exactly what it's doing with that setup and never wastes it on plot that doesn't matter. Art quality tanks in stretches, but the voice acting keeps the chemistry alive through every low-budget scene. This is built for people who want the ecchi and the romance to actually work together, not fight for screen time.
Yuya's life takes a bizarre turn when his new stepsister Mitsuki suddenly starts acting completely out of character. She's flirty, forward, and way too interested in him. The reason: a ghost named Hiyori has hijacked Mitsuki's body and claims she needs to make Yuya fall in love with her before she can reach the afterlife. It's an absurd setup that only gets messier as Hiyori pursues him with zero regard for boundaries while Mitsuki's consciousness fights back from inside her own head. What unfolds is a chaotic romantic comedy where Yuya gets caught between a persistent supernatural pest and his increasingly confused stepsister. The situation forces everyone to navigate some genuinely weird relationship dynamics: How do you reject someone who's technically not the person you're talking to? How does the actual Mitsuki feel watching her body flirt with her brother? The show leans hard into comedic fanservice and absurdist humor, treating the whole premise with a wink rather than seriousness. It's goofy, frequently inappropriate, and committed to milking every awkward scenario the setup provides.