The Chiikawa movie’s source: the Siren Arc, and how to read it

Which story is the Chiikawa movie based on?

According to the official movie site, the film adapts the long story known as the “Siren Arc” (セイレーン編), one of the series’ most popular, under Nagano’s full supervision; Nagano also wrote the screenplay.

• “Siren Arc” is the name Kodansha and the movie site use. Fans also call it the “Island Arc” (島編) or “Mermaid Arc” (人魚編). They all mean the same story.
• The original posts have no chapter titles. Any part names you see online (for example, named after scenes) were made up by fans.

• Official movie site: Introduction(Japanese)

Which volume? Volume 8 (not Volume 7)

The Siren Arc is collected in full in 『ちいかわ なんか小さくてかわいいやつ（8）』 from Kodansha, so this one book covers it from start to finish.

• Volume 8: released Nov 21, 2025, ¥1,375 in Japan. Kodansha says it also has book-only new drawings.
• A boxed special edition with 13 kinds of sticky notes and a notebook came out the same day. The story inside is the same as in the regular edition.
• Volume 7 (Nov 21, 2024) contains the Nightmare (Akumu) Arc, not the island story. It is easy to mix them up.
• We have only checked the Japanese editions.

• Kodansha: Volume 8(Japanese)
• Book guide: which volume has which arc(Japanese)

Read the Siren Arc online, in order

The arc was posted on Nagano’s X account from Mar 15, 2023 to Nov 26, 2023. Chiifan lines up all 96 posts in order as X embeds, 10 per page, so you can read it from the very first post.

• It is the longest story in Chiikawa. 96 is the number of posts we collected, not an official episode count.
• The comic has little text, and much of it is told through expressions, so you can follow a lot of it even if you don’t read Japanese.
• Our page shows Nagano’s original posts; we do not copy or store the comic images.

• Siren Arc from post 1(Japanese)
• Where to read Chiikawa: all story arcs

What is it about? (no spoilers)

It begins when a single flyer falls from the sky, inviting everyone to a “special island.” Chiikawa, Hachiware and Usagi go there for a training camp and get caught up in a mission to defeat the Siren.

• According to the official character page, the Siren is good at singing, travels with mermaids, and attacks the islanders for a certain reason.
• Another key character is Shimajiro (島二郎), the owner of the shop of the same name that Chiikawa finds deep in the forest.
• We’ll stop there: the island’s secret and the ending are best discovered in Volume 8 or the movie.

• Official movie site: Characters(Japanese)

The movie and the “Himitsu-bon” bonus booklet

The movie opened in Japan on Jul 24, 2026. As of Sept 14, 2026, Japanese media reported about 10 million admissions and about ¥14.66 billion at the box office.

• You can enjoy the movie without knowing the comic. Watch first and then read Volume 8, or the other way around; either works.
• The 5th theater bonus, the “Himitsu-bon” (secret book), includes story illustrations Nagano drew while planning the Siren Arc, a manga called “Ode and the Island” (オデと島), and a new essay. Theaters in Japan started handing it out on Sept 19, 2026, while supplies last; no end date was announced.

• Official movie site(Japanese)
• Theater bonuses (official)(Japanese)

Frequently asked questions