I was actually kind of expecting him to show up for the Peekaboo fight, since that match took place in a Sumo Arena. I'm also disappointed he wasn't around for the start of the arc. Pentagon, too. I at least expect him to show up later as Reinforcements for the Justice Chojin.
Sadly, that won't happen. The one-shot was basically a farewell letter to Wolfman.
It explains that he has a seriously injured leg and he can no longer fight. When everyone else went into the regeneration capsules, Wolfman abstained because
he was told by his expert doctor that not even the capsule can heal his injury. In the one-shot, Wolfman has a sumo retirement ceremony but none of the idol chojiin are there because they are recuperating in their capsules. Everybody (Geronimo, curry cook, cubeman, etc) cuts a strand of hair on his head but Kanibase hilariously chops his entire top-knot off!!
It's sad but it seems pretty clear that Yude are giving him a send-off so that they don't have to worry about using him anymore. His final fight against an American Sumo wrestler called "Black Ship" is a belter though!!