A man who longed for a warm family life in his previous existence is reborn into a world of magic as Arsha, the firstborn son of the emperor of a vast empire that rules an entire continent. Despite his privileged position, he is considered the unfortunate prince, as his bloodline disqualifies him from being the legitimate heir to the throne. Relegated to the fringes of the imperial palace and separated from his younger half-siblings, Arsha decides to abandon any claim to the throne. His new goal is to achieve what was impossible in his past life: a loving family. He immerses himself in the neglected art of alchemy, using his free time to pursue his interests in his secluded corner of the palace. His talent in this field is extraordinary, and he even succeeds in creating a sentient being using alchemical methods, a being he names Sephira.

The setting is the Iscalion Empire, a magical realm where political intrigue is as common as spellcraft. Arsha is not a typical power-seeking protagonist; his primary wish is to be called "big brother" by his siblings and to live a peaceful life. However, his status as the emperor's eldest son makes him a target. Suspicious nobles, paranoid about his potential claim to the succession, constantly meddle in his affairs. While he prefers to evade them with childish pretenses or occasionally retaliate, his alchemical experiments draw unwanted attention.

Driven by his memories of modern science and an overflowing talent for alchemy, Arsha’s inventions often have world-shaking potential. He accidentally creates revolutionary technology, which he uses to outmaneuver the very nobles who seek to control him. Despite his attempts to remain uninvolved, his actions begin to unintentionally dominate the imperial succession war. The narrative follows his journey as he navigates a complicated political situation with little formal influence, supported only by his father the emperor and a few loyal aides, while everyone else seems to be against him. Key arcs include his early days of pursuing alchemy in exile, creating Sephira, dealing with an assassination attempt, and eventually clearing up misunderstandings that allow him to finally connect with his younger siblings.