This is pure comedic chaos wearing the skin of the series you know. The monsters that spent the OVA terrorizing you come back as punchlines, and the show treats that tonal whiplash like it's the funniest thing in the world. Ushio and Tora themselves barely survive the absurdity of their own story. It's a victory lap that works because it knows what you came for, then gives you something weirder.
Ushio runs into an odd purple monster that appears to want to help him, while Tora has to contend with a kitten. The OVA closes with a large chase that brings back every monster from the earlier OVA series. As a comically deformed side special, the single episode mixes action and comedy with a touch of horror.