Constance Grail is the 16-year-old daughter of a viscount from the Kingdom of Adelbide, who may look plain and not be wealthy, but whose sincerity is a rare virtue in the cruel and ruthless noble society. However, Constance gets into trouble when she witnesses her fiancé cheat on her, and her romantic rival tries to falsely condemn Constance in public. Silently calling for help, the ghost of Scarlett Castiel appears and answers Constance's call. After taking over Constance's body temporarily, Scarlett turns the tide and saves Constance.
On the next day, Constance wakes up with Scarlett by her side, who demands Constance's help in return. Ten years ago, Scarlett, the daughter of a duke famous for her beauty and charisma, was executed for the attempted assassination of the crown prince's fiancée after he broke up with Scarlett and instead made a viscount's daughter his new fiancée.
However, Scarlett insists that she was framed and now wants to get revenge on the people who had her killed. Reluctantly, Constance sets out to find the truth together with Scarlett and discovers an ongoing conspiracy in the process.
The Holy Grail of Eris (エリスの聖杯, Eris no Sehai) is a Web Serial Novel written by Kujira Tokiwa that was first published online in 2017 on Shousetsuka ni Narou
. Since 2019, its light novel adaptation is published by SB Creative with illustrations by Yu-nagi. In the same year, a manga adaptation by Hinase Momoyama began in Square Enix's Manga Up!.
In 2022, both the light novel and manga series have been picked up by Yen Press in English.
This series provides examples of:
- Assassination Attempt: Scarlett was accused of trying to poison the fiancée of her ex-fiancé, Crown Princess Cecilia Luze. For this, she was eventually executed.
- Better to Die than Be Killed: Lily Orlamunde committed suicide two years before the events of the story begin. Volume 2 reveals that she preferred dying painlessly over being captured and tortured by Daeg Gallus for sticking her nose too deeply.
- Big Damn Heroes:
- The story begins with Scarlett taking over Constance's body to fight for her innocence and instead condemn Pamela Francis and Neil Bronson.
- In the middle of Deborah Darkian's "interrogation", Abigail O'Brian appears and forces Deborah to withdraw. She came just in time to save Constance.
- After Scarlett and Constance identify a Daeg Gallus agent in the latter half of Volume 1, Rudy/Aldous Clayton kills the agent before he can kill Constance.
- At the beginning of Volume 2, Randolph Ulster saves Constance and Kate from José and his goons. He realized near the end of the previous volume that Scarlett secretly called for help.
- Chekhov's Gun:
- In Volume 1, Constance finds Lily Orlamunde's key with a weird imprint. Volume 2 reveals that the key's imprint leads to a place where all the information Lily gathered about Daeg Gallus and their plan to throw Adelbide into a war can be found.
- After Constance leaves the Orlamunde Chapel and returns to the Maurice Orphanage, several orphans appear and say "kiriki kirikuku" to her. According to one of the orphans, Tony, Lily taught them that "spell" and told him to use it on any suspicious people if something happened to her. And if someone reacted badly to this, they should quickly run away. As it turns out, it's a phrase Daeg Gallus members use to identify each other.
- Chekhov's Gunman: Shortly after Amelia Hobbs introduces herself to Constance in Volume 1, her colleague Aldous Clayton appears as well to rein Amelia in. A few chapters later, Aldous appears again to save Constance's life from a Daeg Gallus agent.
- The Conspiracy: The secret organization Daeg Gallus has smuggled Jackal's Paradise, a Fantastic Drug, into Adelbide's noble society for the last ten years. Furthermore, they are linked to Scarlett's death somehow. Volume 2 reveals that their plan was named the "Holy Grail of Eris" and referred to Scarlett. They wanted to start a war between Faris and Adelbide, claiming to want to crown Scarlett as the rightful heir to Adelbide's throne and then turn Adelbide, with its vast rich lands, back into a vassal state of Faris. Scarlett's father and King Adelbide saw through that plan and had to sacrifice Scarlett to save an important noble who was guarding Adelbide's border, while robbing Faris of their reason to start the war.
- Couldn't Find a Pen: In Volume 1, Deborah Darkian has Constance sign an oath in blood before proceding their talk.
- Didn't See That Coming:
- Pamela Francis' plan to publicly humiliate Constance and steal her fiancé would have worked if Constance hadn't been possessed by Scarlett, who knew exactly how to manipulate the public and used her wit and flawless memory to have several witnesses speak up in Constance's favor to instead discredit both Pamela and Constance's fiancé.
- In Volume 1, Deborah Darkian sets Constance up and judges her with her friends in an unfair "investigation" that could have ended very badly for Constance. However, after Randolph learned about Constance's plan to meet Deborah, he quickly asked his friend Abigail O'Brian to come to the tea party and protect Constance. Abigail arrives just in time to fend Deborah and her stooges off.
- In Volume 2, it is revealed that Cecilia never planned to become crown princess. She was sent as a Honey Trap to Enrique and make them their Puppet King. Someone like Scarlett could have simply ignored a viscount's daughter. What no one saw coming was how an offended Scarlett dragged Cecilia out in public and thus drew attention to her. This eventually led to Scarlett's execution, which was definitely not part of the plan, because Scarlett should have become queen.
- Fantastic Drug: Jackal's Paradise, also known as Paradise, Jane or J, is a hallucinogen that was introduced at the time Scarlett was still alive. Its present form is even more potent and addictive, which is why its usage is forbidden in Adelbide.
- He Knows Too Much: José is quickly disposed of by Cecilia in Volume 2 to keep his mouth shut.
- Kick the Dog: After Linus Tudor stabs Teresa Jennings, he tells a visibly confused Teresa that he is going to make it look like self-defense and that he didn't lie when he told her he liked her more than his own wife and her childhood friend, Margot, who Teresa always envied. Because unlike Margot, Teresa is much more uglier and pitiful.
- Off with His Head!: Ten years ago, Scarlett Castiel was executed by a headsman via decapitation.
- Protagonist Title: The Holy Grail of Eris refers to both the protagonist Constance Grail and the Deuteragonist Scarlett Castiel, as in-universe Scarlett liked to use the name "Eris" as her alias. Although in-universe it strictly refers to Scarlett. She was the lynchpin of Daeg Gallus' plan to start a coup and war.
- Public Execution:
- Scarlett was publicly executed on Saint Mark's Square in the Prologue of Volume 1.
- In Volume 3, Constance is set to be executed too.
- Quiet Cry for Help: In Volume 2, after Randolph saves Constance and Kate, he reveals how he knew Constance was in danger: not only is Connie a terrible liar and acted nervously, Connie told Randolph through Scarlett that she supposedly saw Norman Holden at the ball they visited a few days earlier. Norman Holden was a deeply devout man who eventually was killed thirteen years ago, his famous Last Words being "Gods, save me!"
- Spiteful Suicide: In a way. A flashback in Volume 2 reveals that Lily Orlamunde knew her life was doomed, so she rubbed it in Cecilia's face that she knew what Daeg Gallus were planning, then hid what she found out in a safe place and committed suicide before they can get to her.
- Tampering with Food and Drink:
- Scarlett supposedly spiked Crown Princess Cecilia's water jug with poison, for which she was condemned and executed.
- Teresa Jennings drugged her husband Kevin's tea with Paradise, leading to him getting more and more unhinged.
- Title Drop: Halfway through Volume 1, Constance and Scarlett find a key Lily Orlamunde left behind and a note that says "Destroy the Holy Grail of Eris."
- Tricked into Signing: In Volume 1, Deborah Darkian invites Constance to a "tea party", when in fact it's just Deborah and her underlings trying to bully Constance and "punish" her for her insolence. Before they begin their talk, Deborah has Constance sign an oath that she claims is a non-disclosure agreement. What she doesn't mention (and what Constance overlooks because she doesn't read the agreement before signing) is that Constance has to obey all decisions that the investigative committee's majority decide is appropriate.
- Vestigial Empire: Faris was once a mighty empire that almost conquered the entire continent, but over time declined. A few centuries before the story begins, the Principality of East Faris, led by Grand Duke Amadeus, was in a ten-year-long war with the empire before it eventually successfully split off of Faris and became a kingdom in its own right. Grand Duke Amadeus became its first king and named the territory Adelbide.
- You Have Outlived Your Usefulness: Linus Tudor, a noble from Faris, begins an affair with Teresa Jennings and tells her to drug her husband's tea with Paradise, so that they could spend time together. Once Kevin Jennings is completely hooked on Paradise, Linus kills her and removes all evidence.
