Chilly finds himself drawn to Bruno, unaware that it is Princess Brunhild disguised as a man. But after learning of a string of mysterious incidents surrounding her, he begins to suspect someone is working against her. He decides to uncover the truth when something strange occurs within him. Meanwhile, Insomniac is selected as the first goodwill ambassador, and his future fiancée is to be chosen.

Insomniac accepts his engagement to Ellie, the castellan's daughter, but conflicting motives begin to emerge behind the arrangement. During a sword tournament at the castle, Swordsman and Ellie advance to the semifinals, where they face off in a fierce duel. Later, Ellie learns she has been chosen to accompany Insomniac as a knight commander aide on his journey to the Country of Long Nights.

As they journey to the Country of Long Nights, Ellie begins to notice subtle changes in Insomniac, whom she has known since childhood, that leave her uneasy. They arrive in a land where blue flowers bloom, and preparations are underway for the annual Walpurga Eve festival. But beneath its peaceful surface, Insomniac senses an ominous presence, and the country's hidden secrets slowly come to light.

Blue dreams compel Hyrrokkin, queen of the Country of Long Nights, to keep Insomniac from leaving. Princess Kastehelmi, who has grown close to Johann, senses that something isn't right. Meanwhile, after learning a secret about Ellie from one of her handmaids, Insomniac rushes to find her. But as the blue maidens approach Ellie, their presence begins to pull them apart.

The blue maidens continue their efforts to pull Ellie away from Insomniac. As Ellie faces danger, she begins to question her mission. Meanwhile, Insomniac finds himself growing fond of the Country of Long Nights. As the distance between them grows, Ellie discovers feelings she never knew she had. In the Marronnier Kingdom, the brothers prepare for the next goodwill ambassador's departure.

The blue flower spirits are revealed to be the ones keeping Insomniac in the Country of Long Nights. They promised a mysterious visitor to bring him before Saint Walpurga by Walpurga Eve, fearing the calamity of 20 years ago would return if they failed. As the fateful day arrives, Insomniac uncovers the link between the spirits and the royal family. Then the mysterious visitor finally appears.