The story begins with Rain, a merchant, being summoned to the royal castle and accused of treason by the King. The King, influenced by his advisor, believes Rain has been selling state secrets to non-human races like dragons, demons, and vampires, citing his ability to procure rare items from them as proof. Despite Rain's protests that these are simply business partners and the items are acquired through trust, the King remains unconvinced. He declares Rain permanently exiled from the human kingdom and orders his soldiers to seize him. As Rain is dragged away, the King reveals his intention to attack Rain's non-human associates as well, fueling Rain's anger and despair.
Rain awakens bound and disoriented, realizing he's been abandoned in a remote location by the soldiers tasked with his exile. They mock him, suggesting he'll starve or be eaten by monsters. Just as Rain despairs, he is unexpectedly encountered by Tiara, a Dragon Princess he knows. The soldiers, recognizing Tiara as non-human and coveting her large tail, attempt to attack her. Rain warns Tiara that they are enemies, and Tiara, misinterpreting their aggression as a challenge, easily defeats and kills the three soldiers, revealing her true identity as a Dragon Princess, a being of immense power comparable to a Demon Lord.
Tiara invites Rain to her nest, a massive, hollowed-out mountain, and listens to his story. Rain explains he was falsely accused of treason and exiled. Tiara, angered by the injustice, offers Rain a place to stay in her nest, expressing her gratitude for his past help in her own life. To further express her displeasure with the King, Tiara launches a powerful fire magic attack on the human kingdom, a declaration of war.
The attack causes significant damage and alerts the King, who, along with his advisor, deduces that the Dragon Princess is responsible. Believing they have been attacked without provocation, the King mobilizes his army to march south and confront Tiara.
Days pass, and Rain settles into life in Tiara's nest, finding it surprisingly comfortable. He and Tiara acknowledge their mutual reliance: Rain transforms useless monster parts into valuable goods for Tiara, while Tiara provides him with rare monster materials for his trade. Tiara is pleased that Rain's exile has freed him from human kingdom trade restrictions. However, their peaceful existence is shattered when hundreds of human soldiers surround Tiara's nest.
Tiara, unfazed, boasts of her past ability to destroy entire nations and confidently prepares to face the army. Rain, however, recognizes the soldiers' weapons as anti-dragon armaments and warns Tiara. The soldiers, seeing Rain with Tiara, accuse him of betrayal. Tiara easily defeats the soldiers, demonstrating incredible magical control by targeting and killing their commander with a precise lightning arrow, causing the remaining soldiers to flee in terror.
After the battle, Rain realizes that his survival and alliance with Tiara will likely lead to him being declared a wanted criminal in the human kingdom. Tiara, acknowledging this danger, offers to take him to his closest acquaintance, a Vampire Princess, to ensure his safety. They depart by flying on Tiara's dragon form.