Shirō Ryūjōji emerges as a fervent kendo champion whose chance forest encounter with the protagonist sparks unexpected romantic sentiments. His identity, long believed by himself and others to be the family’s second son, unravels to expose his true status as the firstborn heir.

During the initial saga, he dedicates himself to easing the protagonist’s struggles with her inherited destiny. This mission fractures when the vengeful spirit of Daiyu Taiko—an ancestral patriarch of the Ryūjōji line—seizes control of his body. The resulting clash forces the protagonist to confront him directly, dismantling centuries-old vendettas and breaking Daiyu’s hold over him.

In subsequent events, Shirō adopts a quieter demeanor, avoiding conflict yet forging an unlikely alliance with the spirited Bantaro. Together, they strategize to aid the protagonist, culminating in Shirō clashing blades with the formidable Freesia Yagyū, using disciplined kendo techniques to counter her assaults.

Post-conflict, he sustains his bond with Bantaro and transitions into a steadfast, non-romantic role alongside the protagonist. His journey concludes with a tempered acceptance of his lineage, weaving individual transformation into the fabric of enduring relationships.