Even as a child, Jack was blessed by the gods for his incredible courage and valor. Not fearing death, he joined the battle against devilish creatures even as a student of swordsmanship. Since then, his hair had been a shade of blue, and his face bore striking red markings. That's why they called him Sunny Day Jack; he was like a sunny day, illuminating any room with his divine aura and kind nature

However, Jack and his father shared a secret: a family curse passed down through generations to one boy. This curse decreed that a boy could only fall in love once, but that love would be eternal, passionate, and unwavering. The true burden of the curse, though, was that the affected boy would stop at nothing for the object of his affection. Jack, being the eldest son, carried this ancestral weight, despite his older sister Jane being the first-born child

For many years, Jack had believed the gods had freed him from this curse, as he had never met anyone special. He truly thought it was gone, allowing him to focus on his duties as a knight. Although a prince, Jack much preferred the life of a knight, yearning to save and help those in need, even if his princely obligations kept him mostly within the palace walls.

One day, he and his royal family journeyed to the kingdom of Elgrey to forge an alliance, sealed by the marriage of their eldest children: his older sister Jane and Prince Vanrim, He sighed with boredom as he strolled around the castle, casually observing its opulent beauty and the wealth of its owners. The walls were adorned with paintings, and huge windows draped in velvet curtains presented a familiar, uninspiring scene he had witnessed countless times in his own palace.