The theatrical anime film 映画ちいかわ 人魚の島のひみつ (Eiga Chiikawa: Ningyo no Shima no Himitsu – The Secret of the Mermaid Island) has revealed several major updates at once: two new voice cast members, a 90-second trailer, and the official opening song.

New Cast: Shimajiro and Siren

Tsugu Mogami voices Shimajiro (島二郎), the owner of a mysterious shop that Chiikawa happens to encounter deep in the forest. The character is known for being dependable, good at cooking, kind to friends, and fully embodying the charm of an “ike-oji,” or attractive older gentleman.

Minori Suzuki voices Siren (セイレーン), a creature with mysterious singing powers who is attacking the islanders for reasons that have not yet been revealed.

90-Second Trailer

The new trailer gathers the main characters, including Chiikawa looking bewildered after islanders hand over a sasumata weapon, Hachiware fired up and wanting to protect the island, Usagi using a “bin-yoyo” to fight Siren and the mermaids, and Shimajiro calmly eating curry.

Opening Song “Kutsu-zure”

The film’s opening song has been confirmed as a new song titled 「くつずれ」(Kutsu-zure). The lyrics were written by original creator Nagano, and the song is performed by Makoto Tanaka as the character Hachiware.

About the Film

The film adapts the long “Siren Arc” (セイレーン編), one of the longest arcs in Nagano’s original manga. Nagano is fully supervising the production. The story follows Chiikawa and friends after they are invited to an island, where their fun trip turns into a request to defeat Siren, who has been attacking the islanders.

The film is produced by サイピク (Saipiku), directed by Kei Oikawa, and scheduled to open in Japan on July 24, 2026. Toho is distributing the film.

Staff

• Original Work / Script: Nagano
• Director: Kei Oikawa
• Character Design: Tomoko Tsuji
• Concept Art: Masaki Hashimoto
• Prop Design: Takumi Takazuma
• Color Design: Ayaka Nagai
• Art Director: Moe Masaki
• CG Director: Yoshinori Nakano
• Director of Photography: Masaharu Okazaki
• Editing: Ayumu Takahashi
• Sound Director: Masaki Tsuchiya
• Sound Effects: Hiromune Kurahashi (Otonarium)
• Music: Shugo Tokumaru, Riki Kamitsutaru
• Animation Producer: Kan Mizoguchi
• Animation Studio: Saipiku
• Distributor: Toho

Voice Cast

• Chiikawa: Haruka Aoki
• Hachiware: Makoto Tanaka
• Usagi: Ari Ozawa
• Momonga: Yuka Iguchi
• Rakko: Yuma Uchida
• Kurimanju: Takayuki Asai
• Shisa: Miyuri Shimabukuro
• Used Bookstore: Momono Harumi
• Shimajiro: Tsugu Mogami
• Siren: Minori Suzuki

Cast Impressions

Tsugu Mogami said that he and the people around him love Chiikawa very much, so he was extremely happy to receive the role of Shimajiro. He sees the character as a dependable adult with plenty of charm and asked fans to look forward to every corner of the film.

Minori Suzuki said that when she learned she had been cast as Siren, she wanted to shout with joy. She prepared thoroughly by reading the original work in detail and focused on conveying the character’s emotions from Siren’s own perspective, not from the opposing side’s view. She sees Siren as a straightforward character who loves her companions and said this summer will definitely be the “summer of Chiikawa.”

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Source: natalie