Kinnikuman - Muscle Returns

Muscle Returns (マッスル・リターンズ, 1996, Kakutou Ace, Kadokawa Shoten) was a one-shot follow up story set 8 years after Kinnikuman's conclusion. In it, a very powerful Choujin named Buki Boy bursts onto the scene and easily takes out Warsman, Terryman, and Buffaloman, leading to a climatic show down with Kinnikuman. The story contained a few inconsistencies with Kinnikuman Nisei (which began publication two years later), one of which being the appearance of a young Kevin Mask. His mask was different, resembling his father's, and according to his starting age in Nisei (18) he shouldn't have even been born when this story takes place.

The story was edited/fixed and re-released in 2001 in the Jump Remix series. Kevin Mask's look was changed into that of a little boy in school clothes, rather than looking like he was 14 with Robin's armor. Meat, who was supposed to be in suspended animation while the story took place, was replaced by Geronimo. Even with these corrections, it still doesn't fit into Kinnikuman Nisei canon well.