Gen Kawauchi, grandfather to protagonist Shima Kawauchi, assumed guardianship of his grandson following his parents' divorce, openly condemning their prioritization of personal desires over their son’s welfare. Renowned for his infectious cheerfulness, Gen cultivated a nurturing environment for Shima’s upbringing, urging him to embrace authenticity over societal conformity.

After Gen’s death, Shima inherited both his home and belongings. Grief drove Shima into emotional seclusion, a solitude only fractured when he formed an unexpected bond with Isaki, a merman. Gen’s legacy lingers in Shima’s recollections, echoing lessons of self-acceptance and the irreplaceable worth of unguarded human connection.