Bekku Nanaki has just moved to Tokyo from her rural hometown and a boy called Banjou Kizaki saves her from a falling billboard. The next day, she discovers that they are classmates, and that he has a reputation for being involved in various accidents and all sorts of trouble. When he drops his notebook, she discovers the reason why he gets into so much trouble in the first place is because he has been making sure that they don't happen, due to his notebook giving him predictions about the various disasters. Bekku, at first, refuses to believe him, even going so far as to throw the notebook into a canal, but over time comes over to his side and reveals that she too can predict the future using mirrors. Together they work to break fate.
This work contains examples of:
- Cassandra Truth: It's in the title. The final chapter opens up with the Greek myth of Cassandra. By the way, Bekku was a fatalist at first because, due to this trope, her childhood friend Nao died because she didn't believe it when Bekku told her about her own death. This lead to Bekku believing that You Can't Fight Fate.
- Demonic Possession: happens to those who wear Cassandra's Mask.
- Leeroy Jenkins: because he knows that he won't die doing those ridiculous stunts.
- Left Hanging: The ending shows us at the day of Banjou's final prediction - his own death at the age of 20. However, we do not find out if or how he dies.
- Making a Spectacle of Yourself: His glasses are hot pink.
- Magic Mirror: Bekku's prediction medium is a mirror, or rather, any reflective surface. Banjou once made her use the reflection of his eyes to see a prediction.
- Mask of Power: The Cassandra Mask gives its user the power to create evil fates at the price of losing their free will and eventually dying. Supposedly, it was created from the remains of the Greek prophetess Cassandra after she died cursing the people who wouldn't believe her.
- No-Holds-Barred Beatdown: Poor Banjou doesn't get much of a say in the final showdown between Bekku/Cassandra's Mask
- Pillar of Light: When Cassandra's mask is destroyed.
- Short Runner: After eight chapters, it's done.
- You Can't Fight Fate: The counter argument. This counter argument is touted by Makita, who has a tape recorder telling him the exact details of what will happen. He gleefully takes it as a gift from the gods, sets himself up as a "prediction enforcer" and considers what Banjou and Bekku are doing as "unforgivable."