Arc of the island, mermaid, and Siren

While Chiikawa and Shisa study from books, Usagi, Hachiware, and Kurimanju take a break, Momonga and the others take a bath, and finally Hachiware wraps up forest training with Rakko.

Chiikawa, Hachiware, and Usagi pick up a flyer that fell from the sky and are surprised to learn it invites them to the island with a large reward.

Drawn by exclusive food on the island, Chiikawa, Hachiware, and Usagi get excited about bringing study supplies and holding a training camp on the island.

While Chiikawa, Hachiware, and Usagi excitedly talk about food, Rakko surprises them with a paper trick and invites them to outdoor training for a change of pace, delighting the three.

Momonga and Usagi join Chiikawa and Hachiware, who are surprised by a gray crowd heading to the island, as a swan-shaped boat arrives.

On the way to the island aboard a swan boat, Chiikawa studies hard as the boat moves forward, watched over by Hachiware, Usagi, and Rakko.

Chiikawa, Hachiware, and Usagi land on the island and are greeted with songs and dances, treated to tropical-style outfits, and look forward to the food stalls.

Chiikawa, Hachiware, and Usagi join the welcome dance on the island, but Chiikawa feels sick from seasickness. Chiikawa drinks a carbonated drink Hachiware received from an island creature and calms down.

Overwhelmed by the excitement of the island, Kurimanju moves to a quiet shady spot watched over by friends and calms down with yakisoba and a drink.

Hesitant before the long line for fruit parfaits on the island, Chiikawa and the others follow Rakko's teaching, wait patiently in line, and enjoy the long-awaited parfaits.

Chiikawa, Hachiware, and Usagi are guided by a gray creature on the island, enter a hut-like lodge, and play excitedly in hammocks.

Chiikawa, Hachiware, and Usagi happily interact with the residents of the island through dancing, eating, music, and card games.

Chiikawa, Hachiware, and Usagi watch fireworks on the beach at night and try to enter a cave they found.

After finding a boat in the cave, Chiikawa, Hachiware, and Usagi row out together in unison toward the bright water surface.

Chiikawa, Hachiware, and Usagi travel through the cave at night in a small boat, singing and enjoying the scenery, but are startled by a large shadow in the water.

As Chiikawa, Hachiware, and Usagi move forward in a small boat, a large creature appears singing, and a chorus-like exchange with those around it continues.

Chiikawa, Hachiware, and Usagi ride the waves in a small boat but hit a rock and get thrown out.

Around a campfire, Chiikawa, Hachiware, and Usagi recall what happened with the mermaids and realize the attack was due to a misunderstanding on the other side.

Chiikawa, Hachiware, and Usagi talk with the mermaids on the island, learn about how their companions were lost and the scales leading to the settlement, and apologize for the misunderstanding.

At night, Chiikawa, Hachiware, and Usagi try to recall what they saw about mermaids in a picture book, talking together while also wondering about the outcome of the subjugation for a reward.

Accompanied by Chiikawa, Hachiware, and Usagi, Rakko heads to a gathering of the island's residents, where it is revealed that residents are disappearing one after another and they are asked to carry out a subjugation of the culprit.

Chiikawa, Hachiware, and Usagi hear from the island's residents how the reward for the request grew much larger, and seeing a set of local specialties and a friendly bird, they understand the situation.

Led by Rakko, Chiikawa, Hachiware, and Usagi are surrounded by a swarm of small black creatures and then face a giant enemy, freezing in place amid the silence.

As Rakko shows his resolve to face the enemy with this group, Chiikawa and the others are handed weapons one after another by the singing brown residents of the island.

While the tip of the stick Usagi holds breaks, Rakko spends time in a cave with Chiikawa and Hachiware, then reacts to a resounding noise and rushes outside.

Chiikawa, Hachiware, Usagi, and Rakko encounter a large fish holding one of their companions in its mouth near the settlement. Rakko raises a sword to confront it in a tense exchange.

Having fled into a house from a huge red creature, Chiikawa, Hachiware, and Usagi reunite with Rakko and explain the situation. Usagi notices something upon seeing an illustrated guide to legendary creatures on the bookshelf.

A white companion checks rumors about mermaids in a book and learns of a legend of immortality, while a tailed one keeps eating as a yellow warrior asks a crying one to help find the culprit.

After reading a book, Chiikawa and Hachiware find only a sword lying outside and realize their teacher is gone, and are shocked together with Furuhonya.

Worried about their missing friend, Chiikawa, Hachiware, and Usagi join Furuhonya to discuss a plan and guidance for searching a dangerous place.

Chiikawa, Hachiware, and the others search inside a cave, reunite with Usagi and the Furuhonya group to thank them for guiding the way, and try to head to another place.

After spotting a downcast brown pair on the beach, Chiikawa and the others talk through the events surrounding the mermaid and rumors about lives.

As Momonga talks about mermaid rumors while stuffing its cheeks with meat, Chiikawa and Hachiware nod along, then everyone is surprised when a pink kid joins them on the beach.

Chiikawa, Hachiware, Usagi, Momonga, and the bookseller rest outdoors with lunch served on leaf plates and small drinks, then take out candy after eating and get ready to set off again.

Momonga swallows candy with gummy inside and chokes on it, suffering until Chiikawa and the others pat its back to make it spit it out.

A black-haired kid with braids opens the container holding Rakko, who is hung from kelp, checks the contents, and tastes them.

In front of the captured Rakko, the mermaid makes an offer about lives, and a plan is discussed to sink them deep in a cage.

As Chiikawa and the others keep searching by the river, they notice a noise in the bushes and cry out in surprise at the Siren that appears.

Mistaking the creature brought by the black-haired kid with braids for a villain, the kid says they will return what was captured and sings cheerfully inside the cage, but Chiikawa and Hachiware point out the mistake.

As Chiikawa and the others push forward tangled in vines, they are startled by the appearance of a black figure and the strange power of a song.

After fleeing through the forest using vines, the friends reunite and check that everyone is safe, but realize they have been separated from the others.

Hachiware, Usagi, and the bookseller hide in a gap in the rocks and confirm what their tools have in common.

Startled by the changing black fruit, Hachiware, Usagi, and the others flee, noticing the fragility of the white shells, the weakening plants, and a cliff ahead.

When Usagi starts singing on top of the cliff, red-headed birds join in for a chorus, and plants grow large while Momonga and the bookseller watch.

At the crumbling edge of the cliff, Hachiware follows the bookseller's advice and, watched by Usagi and Momonga, moves slightly forward and holds still to endure.

Hachiware moves forward cutting vines but falls, then is pulled up by Usagi and Momonga on the cliff and heads to rejoin the lost friends.

While resting in the forest, Momonga talks to Chiikawa about endless wishes and tries to tempt Chiikawa over the mermaid.

After crossing the suspension bridge, Chiikawa and Momonga walk through the forest singing, but get stung by something like a nut they picked up and get caught.

Momonga drops a belonging on the suspension bridge, the bridge starts to break while Chiikawa is crossing, and the two call out to each other.

When Momonga demands belongings on the suspension bridge, candy flies out, and the large gray monsters below catch it with joy, but the bridge collapses and a red fish-shaped bag falls.

Momonga drops a frame assembled on a hill into the water, suggests a game to Chiikawa of dropping sweets into it, and they tug over eagerness to play.

At Chiikawa's call, Hachiware, Usagi, and Momonga gather and recall how they were saved with the help of the used bookstore owner.

Chiikawa and Hachiware meet a large creature carrying two small ones on its head. Startled and scared, Chiikawa runs away from the spot.

After soothing their throats with candy, Chiikawa and the others try to rescue friends wrapped in vines and hanging, using swords and forked sticks.

Watched over by Hachiware, Chiikawa challenges the vines with the teacher's sword but fails, and the large creature leaves with the friends entangled in vines, leaving Chiikawa behind alone.

Chiikawa moves through the forest and waterfront, stuffing cheeks with red fruit found there while shedding tears.

Lost and crying in the forest, Chiikawa and Hachiware follow signs to reach Shimajiro, the clam soup shop, but the owner tells them business is closed for the day.

Shimajiro serves katsu curry and clam soup to Chiikawa after waking up, and Chiikawa drinks the soup and is surprised by its distinctive clam flavor.

While eating at a shop on the island, Chiikawa hears how a being that suddenly came to the island received food from the people of the island and settled there.

Shimajiro says he has an idea where their friends are, tells Chiikawa about the cave and the mermaid seen underwater, and the two try to go check it out.

Centered on Rakko hanging from kelp, Hachiware, Usagi, Momonga, and the used bookstore owner gather and work together to try to break free.

As rumors of long life tied to the mermaid come up, Rakko, Hachiware, Usagi, and Momonga hanging from seaweed struggle because they hate the darkness of the cage.

At Rakko's signal, Hachiware, Usagi, Momonga, and the used bookstore owner hang from the seaweed and struggle to tear it apart while thrashing around.

The mermaid reties the friends hanging from the torn seaweed and proceeds to prepare them as pickles, letting the savory flavor soak in.

Walking with Shimajiro on a night road, Chiikawa is startled by black creatures with leaves on their heads, but is told they are not enemies and feels relieved and calls out to them.

Chiikawa, Hachiware, and the others join up in the sea and work with Rakko and the used bookstore owner to rescue friends trapped in seaweed and Usagi and Momonga inside pots.

Urged by Rakko, who senses something wrong at the waterfront, the friends flee, and Rakko dives into the water to look for shells.

Urged by Rakko, who notices the water shaking, Chiikawa, Usagi, and the other friends flee the waterfront, and Rakko dives into the water to look for shells.

Unable to understand each other, Shimajiro and a black-and-white creature chase each other underwater, creating a swirling torrent.

As Shisa and Kurimanju share their feelings for the island and Rakko expresses gratitude to the islanders, Chiikawa and Hachiware rush over.

At night, Rakko gathers the islanders and explains that a fellow mermaid was eaten and the Siren is angry, asking for any leads, but the crowd grows restless.

While struggling with how to deal with the Siren, Chiikawa hears Rakko's story and, with Hachiware watching, comes up with the idea of making curry together.

As Chiikawa, Hachiware, and Usagi taste the island's famous curry made by Shisa and Kurimanju, they reflect on once living alongside the singing creatures.

After Kurimanju finishes a spicy curry and the trio tastes it and confirms it is still not as hot as they want, Shisa asks them to gather anything spicy from home.

When Shisa's curry runs short, Chiikawa, Hachiware, and Usagi head to a hut at night to look for more and bring back spicy ingredients shared by Kurimanju.

Momonga tastes the spicy pot Shisa finished at night, turns bright red, and collapses.

Chiikawa, Hachiware, Usagi, Momonga, Shisa, and Kurimanju gather to defend the island, resting Rakko's curry to deepen its flavor and suggesting they freeze it to stay ready.

As suspicion falls on the group over the singing heard at night, Rakko defends its companions while Shisa prepares curry in front of Chiikawa and the others.

Usagi bets everything on the curry, and as Chiikawa, Hachiware, Momonga, and Rakko watch, the Siren with a used bookstore on its head tastes it and harshly criticizes the heat.

As they look back on a fight that used spiciness to their advantage, Shimajiro appears in sumo wrestler attire to everyone's surprise. They are shown puzzled, wondering if they know him.

Encouraged by Shimajiro, who prides himself on flavor, Chiikawa takes out hidden extra-hot chili peppers. While Shimajiro takes on the vines, the mermaid reappears to interfere.

Shisa challenges Shimajiro in sumo wrestler attire but loses and is apologized to by Shimajiro. As they gather around curry, the sword-bearing Shisa shows eagerness for a remaining plan.

They liven things up with Usagi's singing and music played on Kurimanju's cans, and Chiikawa and Momonga join in to try to lure out the red, fish-like creature.

When the singing mermaids lose coordination and grow weaker, Chiikawa and the others launch a counterattack with curry in hand.

Chiikawa is hung up to lure the meat, while Hachiware, Momonga, Usagi, and the others work together to carry out the plan.

As the hanging Chiikawa and Hachiware are joined by Momonga waiting with a frying pan, Rakko checks the blade and cuts the rope to drop them toward Kurimanju waiting below.

Chiikawa and Hachiware charge with meat, joined by Usagi and Momonga in a scuffle with Shimajiro, but in the end they flee in a cloud of dust.

As Rakko silences the other side and gains the upper hand, Chiikawa, Hachiware, and Usagi wonder if their actions are truly right.

While Chiikawa, Hachiware, and Usagi watch, a red fish-like being attacks a small companion, and another companion steps forward to plead with it to stop.

While Chiikawa, Hachiware, and Usagi watch, the red-faced being looks convinced and releases water. Moments later, small brown creatures lie collapsed, shocking everyone.

Chiikawa, Hachiware, and Usagi carry a collapsed octopus-like creature into a room and care for it, checking its breathing while waiting for it to wake up.

Chiikawa, Hachiware, and Usagi visit a leaf-headed creature with Rakko, are treated to soup, recall being protected by it before, then visit again with a thank-you gift and watch over it as it sleeps.

Prompted by something they learned from a book, two leaf-headed beings go fishing by boat and meet a large mermaid and two small mermaids at sea.

As two round leaf-headed beings fish from a small boat while a girl and small creatures swim nearby, a huge shadow appears behind them, and finally a giant red fish bites and breaks the boat.

After feeling something touch them in the sea, they go ashore and meet a collapsed fish and a brown leaf-headed creature. The story shows them looking things up in a book and sleeping close together.

While a mermaid parent and child sleep after eating, a white fish-person nibbles snacks left on the beach, and finally a brown leaf-headed creature is dragged into the bushes.

A round leaf-headed creature nurses a companion lying in bed with a stew, and the story shows the companion sitting up as they eat together and stay close.

Round leaf-headed creatures share bowls containing fish meat, eating with chopsticks in surprise and tears.

Two round leaf-headed creatures notice battery compartments in their bodies, replace the batteries, and sit up in surprise.

Small creatures with leaves on their heads quietly hold hands, but when they see a large white-faced creature eat one of their own, the others scream and cry as they flee in panic.

Surrounding Rakko, Chiikawa, Hachiware, Usagi, Momonga, and Shisa share a meal around a bonfire and talk, toasting the hard work of the friend leaving tomorrow.

Chiikawa and Rakko share drinks around a bonfire with Shimajiro and the island residents, thinking about continuing the search and the mystery surrounding the mermaid.

Chiikawa, Hachiware, Usagi, Momonga, Shisa, and Kurimanju spend a calm evening singing around a large bonfire at night.

Amid a festival around a bonfire, Kurimanju grows thoughtful while immersed in memories with friends. Kurimanju spends time with small creatures with leaves and turns around when spoken to.

As Chiikawa and Hachiware walk along a dark night road singing, they notice small shadows and a large figure in surprise, and soon become surrounded by black shadows.

Chiikawa, Hachiware, and Usagi sing a song before a bonfire at night while the surrounding creatures watch over them.

While walking along a night road, small creatures with leaves meet someone wearing a red mask, take a photo together, and part ways. They then keep walking side by side while humming a song.

They receive clam soup, curry recipes, and other souvenirs from Shimajiro and are seen off by their companions from the island. The white bird thought to be gone turns out to be a lost bird, and they face the morning sea as the time for farewell comes.

After saying goodbye to those who cared for them on the island, Chiikawa and Hachiware pack souvenirs and head home. Usagi, Momonga, Rakko, and Shisa gather for a lively farewell scene.