The anime series was complete crap anyway. Incognito is one of the worst filler villains that I've ever seen.
Now the Ultimate OVA series is infinitely better than the crappy anime series that was released prior to it simply because it actually follows the actual manga.
Watch the Ultimate OVA instead or at least read the manga.
Or you could go off and read the manga and watch the Ultimate OVA series at the same time. Either way, it's a better experience.