Octo-1, known as Tako in its original Japanese iteration, is a compact crimson octopus-form robot engineered by Hiyoshi Goh (alternatively named Little Jon Armstrong in specific adaptations). Functioning as an auxiliary non-combat support unit for the Voltes team, it occasionally earns recognition as the group's "sixth member".

The robot displays a personality marked by fervent eagerness to demonstrate its value and profound loyalty to the Voltes team, especially its creator Hiyoshi. This enthusiasm occasionally triggers unintended complications, such as during a mission where Octo-1's presence coincided with critical damage to Hiyoshi's Volt Machine. The incident temporarily prevented Voltes V formation and led to Kenichi Goh (Steve Armstrong) accusing the robot of causing the malfunction.

Operationally, Octo-1 executes diverse support tasks and errands while possessing flight capability. In a pivotal display of utility, Hiyoshi disassembled the robot during a combat emergency to harvest components for repairing his damaged Volt Machine, later fulfilling his promise to restore Octo-1 fully.

Beyond logistical aid, Octo-1 exhibits communicative traits including Japanese greetings like "Ohayou, konnichiwa" and occasional fourth-wall-breaking address to the audience. Its design and operational framework reflect Hiyoshi's specialized knowledge in robotics and electromagnetism.