Naoji Ishizuki is a Japanese exchange student from a warring country who transfers to Rosenstolz Academy in the fictional European nation of Kuchen. He navigates initial isolation and distrust due to his foreign origins, with cultural practices like preparing his own bento lunches setting him apart from the academy's noble norms.

His development centers on his relationship with Ludwig Herzog von Mohn nahe Liechtenstein (Lui). Their first encounter involves Lui criticizing Naoji's meal, establishing a complex dynamic where Naoji gradually earns acceptance through steadfast dedication. Over three years, Naoji adopts the ritual of serving Lui tea three times daily—morning, noon, and night—symbolizing his commitment and evolving connection.

Naoji experiences moments of jealousy, particularly when observing Lui's closeness with others like his cousin Camus, underscoring his deepening personal investment. His journey progresses from formal interactions to greater intimacy, culminating in Lui granting permission to use the nickname "Lui," reserved for those closest to him, signifying Naoji's hard-earned place at his side.