映画ちいかわ 人魚の島のひみつ (Movie Chiikawa: Secret of the Mermaid Island), the blockbuster anime film that opened on 24 July 2026 and has already surpassed ¥11 billion at the box office, launched its 4DX run on 5 September 2026 at 65 theatres across Japan. This review — written by someone who saw the standard version five times before stepping into the 4DX screening — covers the full range of physical effects added to the experience. Spoilers follow.

Sold Out on Day One

At Grand Cinema Sunshine Ikebukuro in Tokyo, all three 4DX screenings on opening day sold out during the members-only pre-sale window — even faster than the regular screenings. The same day also marked the start of the fourth round of theatre-entry bonuses (mini-charm figures of Shimajiro, Siren, Hitoha, and Futaba), which likely contributed to the rush, but the 4DX seats clearly had a pull all their own.

Safe for First-Timers

Worried that seat vibrations will break your immersion? They won’t. The 4DX effects are dialled back noticeably during quieter, character-focused scenes, so the story comes through just fine. First-time viewers and 4DX newcomers alike can jump straight into the 4DX version without concern.

“Summer Island” Atmosphere, Amplified

The film’s holiday-on-a-tropical-island vibe is one of its greatest charms, and 4DX leans into it hard. During the early ferry scene — where Chiikawa and friends sail toward the island — the seats sway gently, making you feel genuinely aboard a boat. Later, when the trio gathers around a campfire, warm air flows from the headrest area, brushing your cheeks and ears like real heat from the flames.

One hoped-for effect that didn’t materialise (at least at this particular venue) was food scent — no yakisoba or curry aroma accompanied those scenes. That said, reports from other theatres mention floral scents and even soap bubbles, so each venue adds its own flavour.

Siren Feels Enormous — Shimajiro Hits Hard

Action sequences are where 4DX earns its keep. Siren, the film’s largest antagonist, triggers seat vibrations just by moving — the sheer physical presence of the creature is dramatically amplified. The rowboat-chase scene early in the film shakes the seat so violently you’ll want to grip the armrests. Vine attacks are rendered as cold air across the cheeks, and Siren’s entrance is accompanied by stage smoke billowing from beside the screen.

Shimajiro, who faces off against Siren, brings plenty of water-spray moments — diving underwater with Chiikawa on his back, and churning the water in battle. The climactic showdown between the two unleashes vibration, wind, and water simultaneously in what is easily the most intense 4DX sequence in the film.

A personal highlight: the mid-film scene where Hachiware endures a vine assault and then counter-attacks with a sasumata in one hand and Rakko-sensei’s sword in the other. The moment the blade strikes, water sprays directly into your face — leaving you soaked and wondering whether Hachiware secretly uses Water Breathing.

Usagi: The Undisputed 4DX MVP

If one character benefits most from the 4DX treatment, it is Usagi — and it isn’t close. Her signature “prurururu” cry is translated into a rumbling, engine-like vibration. Every time she runs, the seat shakes (Chiikawa and Hachiware running produces no such effect). Her new hand-held weapon — nicknamed “Binyoyo” — even has its recoil reproduced in the seat.

Best of all are Usagi’s two rap sequences: the seat pulses with the beat, letting you feel the rhythm in your whole body. Usagi fans, this version was made for you.

Other Effects and One Important Warning

Other notable moments include the scene where Momonga chokes on a candy and the used-bookstore owner thumps their back — you feel the impact in your own back — and Hitoha’s signature strike, which also gets a physical effect. The film is packed with more surprises than can be listed here.

The one genuine downside: because so much of the story takes place on and around a mermaid island, water spray hits your face constantly. Bring a small towel. Seriously.

Overall, the 4DX version of Movie Chiikawa: Secret of the Mermaid Island is a genuinely immersive way to adventure alongside Chiikawa and friends. Highly recommended — just come prepared to get wet.

Film Details

映画ちいかわ 人魚の島のひみつ

• Release date: 24 July 2026 (IMAX version also launched same day)
• Original story & screenplay: Nagano
• Director: Kei Oikawa
• Character design: Tomoko Tsuji
• Concept art: Masaki Hashimoto
• Prop design: Takumi Kotsuma
• Color design: Ayaka Nagai
• Art director: Moe Masaki
• CG director: Yoshinori Nakano
• Photography director: Masaharu Okazaki
• Editor: Ayumu Takahashi
• Sound director: Masaki Tsuchiya
• Sound effects: Hiromune Kurahashi (Otonarium)
• Music: Shugo Tokumaru / Chikara Kamimizutaru
• Animation producer: Kan Mizoguchi
• Animation studio: Saipic
• Distributor: Toho

Cast

• Chiikawa: Haruka Aoki
• Hachiware: Masato Tanaka
• Usagi: Ari Ozawa
• Momonga: Yuka Iguchi
• Kurimanju: Takayuki Asai
• Rakko: Yuma Uchida
• Shisa: Miyuri Shimabukuro
• Used-Bookstore Owner: Momono Harumi
• Shimajiro: Tsuguo Mogami
• Siren: Minori Suzuki
• Hitoha: Momoka Terasawa
• Futaba: Sayumi Suzushiro