Reading guide
Where Does the Movie Fit in the Manga? Timeline and Reading Order
The movie "Chiikawa: The Secret of Mermaid Island" is based on the Island Arc from volume 8. For the shortest route, read volume 8; in volume order, go from volume 7 to 8; or, following the publication order of the original X posts, read on the Island Arc page.
The Movie's Source Is the Island Arc in Volume 8 | Comes After Volume 7 in Volume Order
The source of the movie "Chiikawa: The Secret of Mermaid Island" is the Island Arc collected in tankobon volume 8, positioned after volume 7 in volume order. As of August 18, 2026, the movie was released on July 24, 2026. If you only want to read the source material, pick up volume 8; if you want to read from earlier volumes, go from volume 7 to volume 8.
The landmark to look for is the arc name "Island Arc" (島編). It is sometimes called the "Siren Arc" or "Mermaid Arc," but when checking which volume contains it, remembering it as the Island Arc in volume 8 is the clearest approach. "Mermaid Island" in the movie title and the Island Arc, the collection name in the tankobon, refer to the same source material.
The Island Arc begins when Chiikawa and Hachiware see a job posting for island work that Usagi has brought. The listing shows a reward a hundred times the usual amount, and also mentions conditions like island-exclusive ramen and sweets, with meals provided free. Huge rewards and the promise of food set the three on a journey across the sea.
The main long-form story collected in volume 8 is the Island Arc, spanning 15 chapters. It moves from the scene where they find the job posting, to preparations for crossing to the island, the welcome on arrival, encounters with the Mermaid and Siren, and the meeting with Shimajiro. For anyone who wants to cover the movie's source material in a single book, volume 8 is a straightforward entry point.
Volume 7, on the other hand, does not contain the Island Arc. Its main contents are four arcs: the Nightmare Arc, the Yamanba Arc, the Uprising Arc, and the Oni Curry Arc. If your goal is just to read the movie's source, volume 8 is enough, but if you follow the tankobon in publication order, reading volume 7 before volume 8 keeps the volume sequence intact.
Volume Order, the Original X Posts, and the Movie Release Are Separate Timelines
When checking "where in the manga" something is, it helps to separate the volume order for reading the story, the publication period of the original X posts, and the movie's release date. In volume order, volume 8 follows volume 7; the original X posts for the Island Arc ran from March 14, 2023 to November 26, 2023; and the movie opened on July 24, 2026. Even though they all point to the same Island Arc, each date stands for something different.
Lined up purely by calendar order: the Island Arc's original X posts in 2023, volume 7's release in 2024, volume 8's release in 2025, and the movie in 2026. But the reading order of the tankobon follows release years and volume numbers, going from volume 7 to volume 8. Looking at the year of the original posts and the volume number containing the Island Arc separately is the quickest way to avoid confusion.
On the original X, the Island Arc spans 130 posts. Rakko joins the group that saw the job posting, they gather at the seaside, and set off for the island on a bird-shaped boat. After arriving, they are welcomed by the islanders and enjoy island-exclusive meals and sweets. Because you can follow the start of the journey post by post, one appeal of the original X is that you can even feel the pacing of the serialization.
Lining up the tankobon dates: volume 7 was released on November 21, 2024, and volume 8 on November 21, 2025. In other words, the Island Arc's original X serialization finished before volume 7 even went on sale, but its place in the books is firmly volume 8, after volume 7. If you judge volume order only by the years the posts were published, this is where things tend to look reversed, so be careful.
The movie was released after the original X serialization ended and after the arc was collected into volume 8. However, just because the movie's release date is recent does not mean you need to look for source material beyond volume 8. What is identified as the movie's source is the Island Arc in volume 8. Simply separate the three clocks, and the dates 2023, 2025, and 2026 connect neatly into a single line.
| Timeline | Position / Date | How to Read |
|---|---|---|
| Tankobon volume order | Volume 8 after volume 7 | To keep the flow, volume 7 → 8 |
| Original X publication | March 14, 2023 – November 26, 2023 | Follow the Island Arc posts in publication order |
| Collection into tankobon | Volume 8, released November 21, 2025 | Read the Island Arc in one book |
| Movie release | July 24, 2026 · Already released | The source's position is volume 8 |
Reading Before the Movie? The Shortest Route Is Volume 8 Alone
If you want to grasp the manga's settings and characters before seeing the movie, reading just volume 8 is the fastest way. In a single book, you can follow the flow of Chiikawa, Hachiware, and Usagi answering the job posting, crossing to the island, enjoying the welcome feast, and then closing in on the strange happenings there. If you would rather not know the ending in advance, you can simply confirm where to read and head straight to the movie.
Reading the manga first lets you understand why they joined the job posting and who traveled to the island together before watching the movie. If you see the movie first, you can open volume 8 afterward and follow the Island Arc in tankobon form. Either way, the volume to read is volume 8. You can decide the order based on how much you want to know and your feelings about spoilers.
Early in the Island Arc, Chiikawa, Hachiware, and Usagi meet a Mermaid on the water from a small boat inside a cave. Just as they are enjoying a song about food, a giant Siren appears and the calm, exploratory mood changes in an instant. This scene establishes how the Mermaid, the Siren, and the island—the key elements of the Island Arc—make their entrances.
If you also want to savor the tankobon's flow, proceed from volume 7 to volume 8. Volume 7 depicts Hachiware's Gekokujo Online and Rakko's training, the encounter with the Yamanba, a spicy curry marked with an oni, and Chiikawa's nightmare, among other stories. The next volume, volume 8, shifts the stage to the island, so reading the two consecutive books reveals the range from everyday life to adventure.
Even if you haven't read volume 7, volume 8 presents the reason for going to the island and the companions, so heading straight into the Island Arc for the movie won't leave you behind at the entrance. The shortest route, volume 8 alone, or the volume-order route from volume 7 to 8—you can choose based on where you want to savor the story's flow.
After the Movie, Trace the Original Post Cards in Publication Order
If you want to check how the original story unfolds after seeing the movie, you can trace the original X post cards in publication order on the Island Arc page. Unlike rereading the story gathered in volume 8, this is a way of reading that advances through the 130 posts one card at a time. You can look back on the serial's divisions as they accumulated, from the job posting to the voyage and the welcome feast.
On the Island Arc page, the original posts are lined up in publication order. You can check, post by post, the moments such as the boat's arrival, the time of the welcome meals, and the instant the atmosphere changes in the cave. If you want to relocate a scene you read in the tankobon, tracing the cards from the top starting at the Island Arc's beginning makes it hard to lose your place.
As the story progresses, it is revealed that islanders are being abducted one after another, and the group is asked to subjugate the culprit. Chiikawa, separated in the forest, meets Shimajiro, who runs a shellfish soup shop, and gains a clue for finding the others. Later, the islanders pitch in too, and a spicy curry-making effort begins with Kurimanju as head chef and Shisa as taster.
Even without stepping into the core ending, this stretch shows that the Island Arc is a long-form story that builds through stages: welcome, strange happenings, search, and countermeasures. After the movie, you can advance in order to the original posts for the characters or scenes that caught your attention and check the surrounding events as well. It is a reading style unique from the tankobon, one that leaves the lingering aftertone of each individual card.
Note that the post cards on the Island Arc page are not a story beyond the movie, but the Island Arc's original posts published in 2023. Don't mistake them for a movie sequel; use them as an entry point for rereading the original in publication order. Read it all at once in volume 8, keep the volume order starting from volume 7, or retrace it card by card. All three paths lead to the same Island Arc.
Frequently asked questions
Which volume is the source of the Chiikawa movie?
The source of the movie "Chiikawa: The Secret of Mermaid Island" is the Island Arc collected in volume 8. In volume order, it comes after volume 7.
Do I need to read volume 7 before seeing the movie?
If you just want the shortest read of the source material, volume 8 is enough. If you want to enjoy the tankobon flow in publication order, go from volume 7 to volume 8.
When were the Island Arc's manga and the movie released?
The original X posts were published from March 14 to November 26, 2023, and the movie was released on July 24, 2026. The publication period of the original posts and the tankobon volume order are separate things.
How can I read the original posts in order after the movie?
You can trace the original X post cards in publication order on the Island Arc page. It is a page for rereading the original posts published in 2023, not a movie sequel.