- Name: Stereo-Cassette King (ステカセキング Sute Kase Kingu)
- Classification: Akuma Choujin
- Homeland: Belgium
- Age: 21
- Height: 214 cm
- Weight: 700 kg
- Chojin Kyodo: 2,500,000 Power
- Trademark Techniques: Devil's Symphony, Choujin Encyclopedia
- Seiyu: Issei Futamata
- First Appearance: Seven Akuma Chojin Arc
Stereo-Cassette King was a choujin based on a Walkman, and the weakest of Buffaloman's henchmen. He was the first of the seven evil chojin to fight Kinnikuman. He could load a cassette into himself which would give him the abilities of a certain choujin (among them Robin Mask, Ramenman, Brocken Jr., and Warsman). This led to his downfall, however, when he used an outdated cassette of Kinnikuman to finish Kin with his own moves, only to learn that despite his silliness, Suguru had greatly improved himself as a Seigi Choujin since beginning his career. Kinnikuman then defeated him with a Kinniku Buster.
Seven years later, Ste-Casse King reappears along the rest of the Seven Akuma Choujin, replacing Warsman in Russia. His opponent in the match is Turboman, which calls him an "outdated home application". On this fight, he seems to have acquired new cassettes, which he uses to dominate during half of the match. After having used Kinnikuman Zebra, Neptuneman and Mammothman cassettes, Ste-Casse decides to end it using Warsman's tape and the Palo Special. Unfortunately, Turboman has the power to "charge" his opponents' power, making them lose control of their moves. Ste-Casse King is ultimately defeated by Turboman's Complete Sting, after having lost his limbs due to overcharging.
- Theme Song
- Secret Cassette Transformation (㊙カセット大変身 Maruhi Casetto Dai Henshin) by Masanori Sato.
- One of the 7 Devil Choujins
- Fight Record
- Fat Pig
- The Chojin with 1,000 Bodies