"Shin Getter Robo vs. Neo Getter Robo" is a four-episode OVA series that serves as a crossover and reimagining of the classic Getter Robo franchise. The story is set in a world where humanity faces existential threats from monstrous creatures known as the Oni, who emerge from a mysterious dimension. To combat this threat, the Saotome Institute develops advanced mecha known as Getter Robos, powered by the enigmatic Getter Rays. The narrative revolves around two distinct teams piloting different versions of the Getter Robo: the Shin Getter Robo team and the Neo Getter Robo team.

The Shin Getter Robo team consists of Ryoma Nagare, Hayato Jin, and Musashi Tomoe, veteran pilots who have faced numerous battles. Their Getter Robo, Shin Getter Robo, is a powerful and experimental machine designed to harness the full potential of Getter Rays. The Neo Getter Robo team, led by Go Ichimonji, Benkei Kuruma, and Gai Daido, operates a newer, more refined version of the Getter Robo, designed to be more stable and efficient. The two teams initially clash due to differing philosophies and approaches to combat, with the Shin Getter team favoring raw power and the Neo Getter team prioritizing control and precision.

As the Oni threat intensifies, the teams are forced to confront their differences and work together. The story explores themes of unity, sacrifice, and the consequences of wielding immense power. The Oni, led by the enigmatic Emperor of Darkness, are revealed to be ancient beings with a deep connection to the Getter Rays, suggesting that the conflict between humanity and the Oni is rooted in a larger cosmic struggle. The series culminates in a climactic battle where both teams combine their strengths to face the Emperor of Darkness and his forces, highlighting the necessity of cooperation in the face of overwhelming odds.

The characters are driven by their personal motivations and past traumas, which influence their actions throughout the series. Ryoma Nagare, the central figure, embodies a hardened warrior mentality, while Go Ichimonji represents a more idealistic and disciplined approach. The interplay between the characters and their respective Getter Robos underscores the series' exploration of human ambition and the ethical dilemmas of technological advancement. The narrative is fast-paced, with a focus on intense mecha battles and the evolving dynamics between the two teams, culminating in a resolution that emphasizes the enduring legacy of the Getter Robo as a symbol of humanity's resilience.