The Ramparts of Ice (Japanese: 氷の城壁, Hepburn: Kōri no Jōheki) is a Japanese web manga series written and illustrated by Kōcha Agasawa. It was first published as a webtoon under the Line Manga Indies section, and after collaborating with the Margaret editorial team, it was picked up for official serialization through the Line Manga digital service from January 2020 to April 2022. Shueisha published its chapters in 14 tankōbon volumes from July 2023 to February 2025.
The series follows Koyuki Hikawa, an introverted high schooler who keeps her distance from others, until three of her schoolmates draw her out and help her enjoy her adolescence to the fullest.
The first season of an anime television series adaptation produced by Studio Kai aired from April to July 2026. The second season premiered in October of the same year.
Contents
Synopsis
High school student Koyuki Hikawa has trouble interacting with others, instead preferring to keep her distance and spend her time alone. However, when she meets Minato Amamiya, he suddenly starts trying to close the distance between them.
Characters
Main
Koyuki Hikawa (氷川 小雪, Hikawa Koyuki)
Voiced by: Anna Nagase (Japanese); Erika Harlacher (English)
A reserved high school student who keeps her distance from most people, except her friend Miki, maintaining a cold exterior that earns her the nickname "The Ice Queen" among classmates. This demeanor stems from past teasing by boys about her short stature. Over time, she grows more open through her friendship with Miki and her relationships with Yota and Minato. Her limited social experience causes her to overthink her words, resulting in awkward moments. Initially intimidated by Minato's outgoing nature, she eventually develops feelings for him, but is heartbroken when he briefly dates Momoka Kuriki, whose emotional abuse echoes her middle school experiences. Despite this, she still tries to help him overcome his fears and express his feelings more openly, even though initially, Minato tries to push her away. When Minato returns and confesses his feelings, she reciprocates.
Miki Azumi (安曇 美姫, Azumi Miki)
Voiced by: Fūka Izumi (Japanese); Brianna Knickerbocker (English)
Koyuki's childhood best friend known since elementary school. She compulsively seeks to please others and maintain a favorable image, concealing a rowdier nature behind a friendly exterior. This earns her the label of class idol, which she dislikes. Consequently, she limits interactions with Koyuki at school until Koyuki befriends the boys. Miki initially distrusts Minato due to his reputation as an insincere romantic partner and fears his pushy behavior will hurt Koyuki. As Minato learns from his mistakes and grows closer to them, she warms to him. Initially unaware of Yota's feelings, she rejects him when unsure of her own, but eventually recognizes her love for him and reciprocates.
Minato Amamiya (雨宮 湊, Amamiya Minato)
Voiced by: Shōya Chiba (Japanese); Kyle McCarley (English)
Part of the school's "loud group". He believes that he can solve everyone's problems, a mindset he likens to "unlocking" people with keys. This draws him to Koyuki, whom he regards as a particularly difficult case, and he befriends her despite her efforts to avoid him. His behavior earns him a reputation for insincerity, and he inadvertently becomes a player in his romantic relationships. After Koyuki confronts him over his actions, he recognizes his mistakes and becomes more genuine while befriending the girls. He falls in love with Koyuki but conceals it out of fear of rejection, briefly dating Momoka Kuriki, who loves him, before ending the relationship upon realizing he is only masking his fear of loneliness. After Koyuki helps him overcome his fears and self-hatred, he confesses his love, which she accepts.
Supporting
Tsubasa Igarashi (五十嵐 翼, Igarashi Tsubasa)
Voiced by: Chiaki Kobayashi (Japanese); Ryan Colt Levy (English)
A soccer team member who was classmates with Koyuki and Miki in middle school, and is Koyuki's ex-boyfriend. Due to the bullying and trauma she experienced in her past, and how other girls constantly accused her of having a crush on him, despite her vehement denials, Koyuki has become afraid of him.
Tsukiko Shimojima (霜島月子, Shimojima Tsukiko)
Voiced by: Sakura Shinfuku (Japanese); Kayli Mills (English)
Koyuki's classmate and a member of the art club, whom she befriends when they both get put on library duty. She often acts as an audience surrogate, particularly in the burgeoning relationship between Koyuki and Minato, which she immediately deduces. Nevertheless, she is very supportive of them.
Momoka Kuriki (栗木桃香, Kuriki Momoka)
Voiced by: Akari Kitō (Japanese); Laura Stahl (English)
An antagonistic student that joins Koyuki's high school. She hides her true malicious and manipulative self under a friendly and bubbly person, as she pretends to befriend others around her, only to use those "friendships" to ruin other relationships. She is in love with Minato, which leads to her fully resenting Koyuki with a passion, as Minato's obvious crush on Koyuki enrages her. Her crush on Minato slowly turns into an obsession later on when he starts briefly dating her, and her bullying and abusive behavior towards Koyuki only escalates further. His lack of feelings for her, however, weighs on her the longer the relationship lasts. He eventually breaks up with her, which leaves her emotionally unstable. Nevertheless, she vows to work on herself, to become a better person, and to avoid repeating the same mistakes she made while dating him.
Yūki Azumi (安曇優希, Azumi Yūki)
Media
Manga
Written and illustrated by Kōcha Agasawa, The Ramparts of Ice began publication as a self-published webtoon under the Line Manga Indies section for about two years, before the author was contacted by the Margaret editorial department, who facilitated its official serialization through Line's Line Manga digital service, being published from January 10, 2020, to April 28, 2022. Shueisha published the manga in print, under its Jump Comics imprint, with 14 tankōbon volumes released from July 4, 2023, to February 4, 2025.
The series is published in English on NTT Solmare's MangaPlaza website.
Anime
In January 2025, it was announced that the manga would receive an anime television series adaptation. It is produced by Studio Kai and directed by Mankyū, with series composition by Yasuhiro Nakanishi, characters designed by Miki Ogino, and music composed by Kanade Sakuma and Natsumi Tabuchi. The series aired from April 2 to July 2, 2026, on TBS and its affiliates. The opening theme song is "Tōmei" (透明; 'Invisible'), performed by Novelbright, while the ending theme song is "Sakasama" (逆様; 'Upside Down'), performed by Polkadot Stingray. Netflix is streaming the series globally.
Following the airing of the final episode of the first season, a second season was announced, which premiered on October 1 of the same year. The opening theme song is "Escort" (エスコート), performed by The Beat Garden, while the ending theme song is "Hanakage" (花蔭), performed by Superfly.
Reception
Before its serialization, The Ramparts of Ice received a special prize at the "Shueisha Shōjo Manga Grand Prix Powered by Line Manga Indies 2018 Summer". It ranked nineteenth in the web category at the seventh Next Manga Awards in 2021. It ranked first in the Comic CMoa Annual Ranking's josei manga category in 2022. It ranked second in AnimeJapan's sixth "Most Wanted Anime Adaptation" poll in 2023. It was nominated for the 69th Shogakukan Manga Award in 2023. It ranked fifteenth, along with The JoJoLands, on Takarajimasha's Kono Manga ga Sugoi! list of best manga of 2024 for male readers. It was ranked sixth in the Nationwide Bookstore Employees Recommended Comics of 2024 list. The series won the 2024 Vertical Manga Award in the completed comic category.