Suikakujū acts as a demon champion for the Queen of Demons, dedicated to stopping the emergence of the Chōjin (Overfiend). He believes the Overfiend's rise would unleash apocalyptic destruction upon all dimensions, not unity, and strives to maintain the separation of the human, demon, and man-beast realms.

Within the manga, he operates through a faction of reptilian/amphibian demons, devising schemes to capture or destroy the Chōjin. These plans consistently end in catastrophic failure. His portrayal here is overtly antagonistic, fueled by rivalry with the Great Elder and a romantic entanglement with the Queen, who is the Elder's estranged wife. The anime recasts him as a tragic figure with noble intentions, a well-intentioned extremist prepared to inflict vast suffering to preserve existence itself. This includes triggering the 1923 Great Kantō Earthquake in an attempt to disrupt the Chōjin's prophesied arrival.

Suikakujū commands absolute loyalty from his two concubines, Fukakuki and Enkakuki, embodiments of wind and flame respectively and exclusive to the anime. Following his defeat or near-death, they sacrifice themselves in a ritual of tentacled absorption and ecstatic union to restore his power, costing them their lives. Post-revival, he gains tentacular appendages, though their use remains minimal, primarily seen during the concubines' sacrifice.

His sister Yoenki, appearing only in the anime, survives the merging realms. Manipulated by the antagonist Münchhausen II into believing Amano Jyaku caused Suikakujū's death, she seeks vengeance. Suikakujū's ultimate fate diverges: the manga concludes with his death during the conflicts surrounding the Chōjin, while the anime extends his arc into later sequels where he continues to oppose the Overfiend's cataclysmic influence.