The Holy Grail of Eris (Japanese: エリスの聖杯, Hepburn: Erisu no Seihai) is a Japanese light novel series written by Kujira Tokiwa and illustrated by Yuunagi. It was serialized online from October 2017 to August 2018 on the user-generated novel publishing website Shōsetsuka ni Narō. It was later acquired by SB Creative, who have published four volumes from November 2019 to March 2022 under their GA Novel imprint. A manga adaptation with art by Hinase Momoyama has been serialized online via Square Enix's Manga Up! website since November 2019 and been collected in fourteen tankōbon volumes. A new edition of the light novel series by the same author and illustrator was published in five volumes by Drecom Media in November 2024 under their DRE Novels imprint. A sixth volume and a digital short story collection were released in January 2026. An anime television series adaptation produced by Ashi Productions aired from January to March 2026.
Contents
Plot
A decade ago, Scarlett Castiel was executed for supposedly trying to poison the prince's lover. In the present, Constance Grail becomes involved with helping the ghost of Scarlett figure out the chain of events that led to her death. As a result, both of them eventually discover a conspiracy that involves nations.
Characters
Constance Grail (コンスタンス・グレイル, Konsutansu Gureiru)
Voiced by: Kana Ichinose
A kind-hearted low-ranked noble. She was almost vilified at a party, until Scarlett briefly possessed her to humiliate and expose the one who had framed Constance for "stealing" her treasured hairpin. She does not get along with nobles who look down on commoners and loathes baseless gossip. She makes it her life's mission to assist Scarlett in getting her vengeance.
Scarlett Castiel (スカーレット・カスティエル, Sukāretto Kasutieru)
Voiced by: Sayumi Suzushiro
A restless ghost seeking answers as to why she was killed, believing that she had done nothing to warrant execution a decade ago at just sixteen years of age. Haughty but brilliant and open-minded, Scarlett gives Constance leads on people she knew.
Randolph Ulster (ランドルフ・アルスター, Randorufu Arusutā)
Voiced by: Yōhei Azakami
Randolph was Lily's husband until her untimely death and ended up engaged to Constance and helped her with investigating Scarlett's case. He was the first person to learn about Scarlett's ghost. As time goes by, he ends up developing genuine feelings for Constance.
Lily Orlamunde (リリィ・オーラミュンデ, Riryi Ōramyunde)
Voiced by: M.A.O
Lily was a nun of the church and helped many orphaned children. When she was later found dead, it was believed that she committed suicide, albeit some believed otherwise.
Cecilia Adelbide (セシリア・アデルバイド, Seshiria Aderubaido)
Media
Light novels
Written by Kujira Tokiwa, The Holy Grail of Eris was serialized online on the user-generated novel publishing website Shōsetsuka ni Narō from October 16, 2017, to August 4, 2018. It was later acquired by SB Creative who published four volumes with illustrations by Yuunagi under their GA Novel imprint from November 14, 2019, to March 12, 2022.
A new edition under Drecom Media's DRE Novels light novel imprint was published with five volumes releasing on November 7, 2024. A sixth volume and a digital short story collection were released on January 7, 2026.
The series is licensed in North America by Yen Press.
Manga
A manga adaptation illustrated by Hinase Momoyama began serialization on Square Enix's Manga Up! manga website and app on November 3, 2019. The manga's chapters have been collected into fourteen tankōbon volumes as of January 2026. The manga adaptation is also licensed in North America by Yen Press.
A sequel manga illustrated by S.Kosugi, titled Eris no Seihai S, published its "0th" chapter on Drecom Media's DRE Comics website on October 18, 2024. It later began serialization on November 1, 2024. The sequel's chapters have been collected into three tankōbon volumes as of March 2026.
Anime
An anime adaptation was announced on October 20, 2024, which was later revealed to be a television series produced by Ashi Productions (with Good Smile Film and DRE Pictures handling general production) and directed by Morita to Junpei, with series composition and episode scripts written by Kenichi Yamashita and characters designed by Chie Kawaguchi. The series aired from January 8 to March 26, 2026, on TBS and its affiliates, as well as BS11. The opening theme song is "Happy Ever After feat. Yu-ka" (Happy Ever After feat. 由薫), performed by Reina Washio, and the ending theme song is "Camellia" (カメリア, Kameria), performed by Yukari Tamura.
Crunchyroll is streaming the series. Plus Media Networks Asia licensed the series in Southeast Asia and broadcasts it on Aniplus Asia.