Live action TV
Description
The Kujira-Kaijin, also called the Whale Mutant, is a creature of the evil organization Gorgom, designed with the traits of a whale. Unlike many of Gorgom’s other monsters, it is capable of human speech and displays a distinct emotional depth. The mutant possesses a profound love for the ocean, and this attachment becomes the core of its motivations. Upon overhearing that Gorgom’s plans for world domination would inevitably lead to the pollution and destruction of the seas, it grows disillusioned and resolves to betray the organization.

The creature is initially recruited by the high priest Baraom to assist in eliminating Kamen Rider Black. During a confrontation, Baraom learns of the mutant’s treacherous intentions and attempts to kill both it and Black. However, the Kujira-Kaijin manages to break free from Baraom's attack and helps Black defeat the priest, cementing its newfound alliance with the hero. From that point, it becomes a valued ally, offering support against Gorgom.

Following a later battle in which Black is seemingly killed by Shadow Moon, the Kujira-Kaijin retrieves the fallen hero’s body from the sea. Using a secret, clan‑guarded substance known as the essence of life, it performs a revival ritual inside a sacred sea cave, successfully restoring Black to life. The mutant then guides the resurrected hero toward Gorgom’s temple for the final confrontation. Before they can reach their destination, the pair is ambushed by the Togeuo Kaijin. The Kujira-Kaijin is defeated in the ensuing fight and, with its dying words, entreats Black to protect the ocean.

In terms of abilities, the mutant can emit a sticky white foam from the top of its head, capable of immobilizing enemies. It also unleashes disorienting sonic waves from its mouth, and it is fully adapted for underwater activity. Its possession of the life‑restoring elixir, a hereditary treasure of its kind, is perhaps its most significant contribution to the storyline. Throughout its arc, the Kujira-Kaijin evolves from a reluctant enforcer of Gorgom’s will into a tragic, self‑sacrificing protector of the natural world, driven by its unconditional devotion to the sea.