Taiyō is deeply rooted in viticulture, specifically cultivating grapes. He becomes central to a mystery when his prized grape seedling, the "Sapphire Roman," vanishes. This seedling produces grapes renowned for their legendary flavor, highlighting its immense value and Taiyō's dedicated work.

His background includes a childhood friendship with Megumi, forged near a grape orchard. Their reunion reignites this shared history, intrinsically linked to the orchard setting.

Within the mystery narrative, Taiyō's focus is the disappearance of the Sapphire Roman seedling, positioning him as a cultivator determined to preserve or recover this unique agricultural asset.