The Villainess and the Demon Knight manga volume 1 features story by Nekota and art by Seikan.

When noblewoman Cecilia realizes she’s been reincarnated into an otome game, her shock is further complicated by the fact that she’s the villainess! What’s worse, she can’t seem to change her fate. Now, her engagement is broken off, the heroine is harassing her, and she’s forced to work in a brothel—where her very first customer turns out to be the debauched Leader of the Imperial Guard, Lucas Herbst. This dangerous Casanova looks like he’ll be the end of her, until he takes her as a fiancée!

The Villainess and the Demon Knight manga volume 2 features story by Nekota and art by Seikan.

Marquise Cecelia has awoken in the bedroom of the infamous Demon Knight, Lucas Herbst. His rough style of love has left the night before a blur, but apparently he's claimed her as his fiancée! Political shake ups have saved her from disgrace and losing her status. But Lucas's warped love will keep her on her toes... or her back...

The Villainess and the Demon Knight manga volume 3 features story by Nekota and art by Seikan.

Marquise Cecilia is engaged to Lord Lucas, second prince in line for the throne and wielder of the fabled magic sword Eckesachs. Despite being rough in the bedroom, he's completely devoted to her. But while Lord Lucas is busy battling dangerous magical beasts, Cecilia's ex, the former second prince Felix, arrives unannounced. He's unable to accept his treatment of Cecilia is what lost him his inheritance. He places the blame on Cecilia and attacks her! Will the protection magic around Cecilia hold out until Lucas returns? Or will she be at the mercy of Felix's violent temper?!

The Villainess and the Demon Knight manga volume 4 features story by Nekota and art by Seikan.

Cecilia has been reincarnated as the villainess of a dating sim. Now she's married to dangerous Lord Lucas, and her nights are now filled with lustful passion. While the two of them enjoy their newlywed status, Lucas's brother, Prince Leon, has his own wedding plans. The brothers must head to the desert country of Magyar to welcome Leon's future bride. Left alone, Cecilia finds herself unexpectedly playing hostess to the Magyar's handsome prince Akim. This will put her diplomacy skills to the ultimate test!