During a visit to ancestral graves with his wife Kyoko, Ryuuichirou Shiba witnessed two battling oni nearby. The victor, Senki, telepathically entrusted the couple with an infant, vowing to reclaim the child in 15 years. Despite reservations, Ryuuichirou and Kyoko raised the baby, naming him Jiro Shutendo—adapting the demonic title "Shuten Doji" to "Heaven Hand Child" to soften its connotations while honoring his origins. They deliberately withheld their Shiba surname, acknowledging Jiro's temporary place in their home.

Early signs of Jiro's supernatural nature, including a manifested demonic shadow, drove Ryuuichirou to meticulously research oni folklore, mythology, and paranormal phenomena. He pursued academic and spiritual insights to shield his adoptive son and family from heritage-linked threats, poring over historical texts and demonic legends.

At Jiro’s adolescence, Senki’s return triggered chaos: the oni abducted Jiro, and Kyoko suffered a psychological collapse. Institutionalized, she obsessively painted oni murals across her facility’s walls. Ryuuichirou deduced these artworks trapped her soul in a demonic realm. He shattered the paintings with a sledgehammer, freeing her spirit and enabling her recovery.

After these events, Ryuuichirou formally adopted Jiro, bestowing the Shiba surname to permanently integrate him into their lineage. Throughout these trials, Ryuuichirou consistently exhibited protective resolve, analytical rigor, and steadfast dedication to both his wife and adoptive son.