Joshua Grant attends St. Alphonso Academy as a student representative, labeled one of the "marginal princes" due to his origins from a border territory. His royal lineage includes King Cardiss I as his uncle and a distant kinship to King Alphonso, verified by a family-owned coronation painting of Alphonso displayed at the academy. This connection grants him a physical resemblance to Alphonso. Joshua's father, the king's brother, abandoned royalty to marry his mother but died when Joshua was five. His mother succumbed to depression, passing when he was eight, leaving Joshua as the sole heir to the throne. He avoids discussing this past, embracing school life for freedom and normalcy.

Known for an exceptionally gentlemanly and kind nature, he consistently displays a soft heart and concern for others, frequently intervening to resolve peer conflicts. He develops strong affection for Yuuta soon after Yuuta's arrival, notably defending him against accusations of stealing a diamond. This diamond held profound personal significance, its color matching the eyes of Joshua and his late mother, symbolizing his bond to her.

Beyond academics, he enjoys horseback riding. He also performs in academy musicals, delivering dramatic songs that transition into elaborate surreal sequences—shifting from school settings to abstract scenes like confinement in a basement or war-torn landscapes.