In the city of Ert'Aria lives the young inventor Leicester Maycraft. He is part of a small adventuring clan called Oasis led by Carina Verritti, the daughter of the Archduke who rules over the city. Later that evening there is to be a regular meteor shower that comes once every seven years, and the clan is preparing a party. They meet a young puppeteer named Agnes Boulange who makes an impressive show of her magical automata puppets in the square. They also meet a young knight named Chelsea Arcot and the sisters Ritos and Salsa who run the Tortilla shop in front of their clan hall.

The young girl calls Leicester "Papa", which scandalises Carina, but it turns out that the girl, named Minette, is actually a highly sophisticated automaton created by Agnes's mentor, Mize Altowirz, activated by the burst of Ale energy from the meteor, and bonded with him as he was the first person she saw.

Agnes and Leicester are planning something secretly, and later they propose that the clan take on a quest to recover some rainbow flowers that absorb all the light surrounding them. They grow in a certain forest which is growing darker and more dangerous as they flourish. Carina accepts, and they travel to that forest, and Carina and Leicester use her staff Montecchia to survey the area and tell the rest of the clan where to go. Their aerial survey discovers the spot where the flowers grow, and they direct everyone else where it is, while the two of them investigate ahead. As Carina tries to reach for one of the flowers they are attacked by a crystal monster, and she uses her staff to fly to a safe distance so she can use her magic on it while Leicester tries to fend it off, but she suddenly loses magical energy and falls on top of him, and the two of them are tangled in vines in a compromising position when the rest of the clan arrives and defeats the monster, recovering its crystal.

The clan is going on another quest from an old woman who is one of Agnes's most avid fans. They are to obtain a supply of hot spring crystals and go to an abandoned mine to obtain some. While mining these crystals they happen upon a hidden chamber with a large crystal in its centre, which has a complex flow of Ale energy emanating from it. Before they can examine it further the mine experiences subsidence due to the rains, and the ceiling cracks, and they try to get out, but Agnes and Leicester are separated from the others by a cave-in. The two of them manage to find another way out, and see a rainbow at the exit, and rejoin the others.

Oasis has no quests assigned, but everyone is very busy, so no one is around to play with Minette, except Garnet, who suddenly materialises as she was getting bored in the dragon world. Nina asks Minette to buy the ingredients for the night's dinner, which she happily does, considering it as her own personal quest for the day. The Tortilla sisters have also been asked to silently watch her and make sure that she is all right.

The Archduke has organised a party to honour the Knights for their service to the city. Leicester and Nick have been given guard duty for that night over the artefacts at the cathedral which the Knights are supposed to protect. Leicester sees a great sword known as the Sacred Celestine and feels particularly attracted to it, fascinated in its construction by the ancients. The Tortillas have been given guard duty outside the Archduke's palace, and as the party is going on, they are attacked by a crystal monster that seems to have the shape of a serpent. It can move so quickly when it attacks that its movements cannot be seen, so much so that no one can hit it. Minette summons Garnet who is sent to call for Leicester at the cathedral, and when he finally arrives he realises that the monster is attracted by light, so he uses a strong crystal-powered lamp to attract it and allow Chelsea to destroy it. How or why the monster could have appeared in the middle of the city is a mystery.

It has been some time but apparently the Ale meteor shower is still going on. This concerns the Archduke so he sends Oasis on a new quest to investigate the phenomenon. They are asked to visit the forest home of Mise Altoise, Agnes's teacher for possible clues. Agnes is familiar with the area and knows how to get through the maze of magical traps her teacher had set, but notices that they have been changed in subtle ways, so she expects Mise to be there, and is disappointed to find that she is not there. Oasis searches the house and finds a note for Agnes hidden in a secret compartment. Meanwhile, Nick, standing guard outside the house is attacked by a girl who proves to have exceptional fighting ability.

It is the Ert'Aria harvest festival, and to let Minette enjoy herself during the festivities, someone has to accompany her in case Aberdeen strikes again. The Tortilla sisters accompany her through most of the festival, and they see Agnes at her puppet show, Chelsea at the Knights' Cafe, and Carina at the cathedral looking over the artefacts. The Tortillas obtain an item from Leicester they need for the fireworks display that evening. Leicester brings Salsa back to Oasis to obtain an item from Nina, and is invited to join the rest of Oasis to watch the fireworks at the cathedral roof but instead opts to join Ritos to do the fireworks.

Nagan, Leicester's father, explains about how the meteor shower activity that year is rather unusual, and how the previous shower was similar, and that Altoise had been aware of this and trying to investigate it. The letter she left for Agnes mentioned something called the 'Waterwheel of the Heavens', and how it was related to the mysterious meteor shower activity. Carina and Agnes research this mysterious artefact, but find nothing new. Meanwhile, Minette meets with her friend Miriam again, and she says that she wants to give a present to her cat. Leicester suggests they give it a bell that uses an Ale Crystal. The two of them help Leicester make these bells, but as they are finishing Miriam collapses just as a meteor shower falls on the city. It is seen that Miriam is an automaton, and Aberdeen's sister. He arrives with Avril to take her home.

Before leaving, Aberdeen says that he wants the Minette's core, the Anima Pearl, to save Miriam, whose own automaton core is being badly affected by the instability of Ale flow in the world. This leaves Minette conflicted, as she wants to save Minette but her own passing would leave many unhappy, Miriam first of all. Oasis then goes about attempting to find Aberdeen and protect Minette from him, while at the research into the Ale instability left to the Tortilla sisters, who find that the strange phenomena are concentrated around the old mine where they had found the chamber with the large crystal. That evening, Minette resolves to give herself up to Aberdeen to save Miriam, leaving the bells they had made with Leicester at everyone's door. She meets Shelley at the Cathedral who speaks to her briefly about her decision. Leicester awakens and realises that Minette has left, and he goes to find her.

Leicester and the rest of Oasis search the city to try to find Minette. Carina and Leicester are the first to find Aberdeen's home. They are attacked by Avril, but Carina uses a spell to send Leicester ahead to the house while she fights Avril. He confronts Aberdeen and they do battle, and after Leicester makes his weapon produce an explosion that sends both of them reeling convinces him that there has to be another way, a way to save Miriam without needing to sacrifice Minette.

Oasis and Aberdeen and Avril arrive at the mine, and are attacked by a horde of crystal monsters. Aberdeen and Avril remain nearby to repel as many of the monsters as they can as Oasis goes ahead. They appear before a great tower where the Waterwheel of the Heavens is. They are attacked by yet more monsters as they ascend the tower, so Nick and Garnet remain behind to keep the monsters from following.