The twenty-sixth and final episode of Thunder Mask.
- 11th-Hour Superpower: The Increase Machine of Planet Thunder infuses one million volts of electricity into the crippled Koichi's body, restoring his sight and enabling him to transform again.
- Back for the Finale: Rin, Koichi's younger sister, returns to provide him with the Increase Machine.
- Behemoth Battle: Thunder Mask vs. Tetsujin 13 and Bem King.
- Bittersweet Ending: Thunder Mask wipes out Bem King, Dekanda and their forces, but it is implied that the Increase Machine did indeed kill him, since he disappears with Bem King and remains only as the star in the sky he had told Mayumi and Katsuya to watch out for. That said, though there was never a follow-up, just ask contemporary toku heroes how long death sticks for them.
- Darkest Hour: As a result of Thunder Mask being accidentally struck by one of the Science Team's monster-killing missiles, Koichi has been blinded and is unable to transform again lest he die, with the Science Team believing Thunder Mask to be dead whilst the villains, stronger than ever, prepare to finally kill our hero and conquer the Earth.
- Deadly Upgrade: The Increase Machine is said to grant Koichi only three more minutes as Thunder Mask before it kills him.
- Defeat Equals Explosion: Befalls Tokagerus and Dekanda.
- Make My Monster Grow: Averted in the case of Tokagerus, who is destroyed by Thunder Mask before the Behemoth Battle.
- Monster of the Week: Immortal Devil Beast Tokagerus
