When an overworked office worker wakes up, she finds herself in the world of her favorite otome game, “Falling Stars: Astrolabe of Love.” And what’s more, she’s reincarnated as Diana, the villainess! On top of that, Prince Sirius, the character she’s trying to win over, approaches Diana, the villainess, not Chris, the game’s heroine...!

When the villainess and Sirius get together, there will be a Bad End. Diana, who knows the truth about the game, struggles to keep Sirius away from her. However, Sirius refuses to give up. Diana has no choice but to try to force Sirius and Chris together.

Diana has been hit by Sirius's passionate feelings. But, despite her mixed feelings, Sirius still makes her heart race. So then, to find out why the prince is in love with the villainess, she visits a place they seem to have shared a significant memory.

A mysterious envelope arrives with a cryptic message, but Diana ignores it and goes to sleep. When she wakes up the next day, the person sleeping next to her is... Spica, Diana's cousin, and another of Chris's targets. With his appearance, Sirius's behavior is different from usual... is there turmoil on the horizon?

Diana is locked in a prison by Spica. Not understanding why she was trapped there, she searches her cell and finds Diana's diary. What's more, there was a shocking truth written in it! Meanwhile, Sirius, who came to the Diafell household to see Diana, feels something is off when Diana is not there.

Diana is brought to the castle by Sirius, as their shadows gradually overlap. Meanwhile, Spica grieves as he stares at the empty prison Diana left behind. Just then, Spica gets some surprising new information from his servant.

Diana is joined with Sirius in the end. She tells herself that this is the first and last time she will be happy with him. The following morning, Diana tries to say that she will keep her distance from Sirius. But suddenly, Spica and his servant come barging in.

Sirius asks Diana about the Diafell family's plans. She gives up and decides to reveal everything to Sirius and face her punishment. However, Sirius makes a surprising proposal to Diana.