Tiger and Bunny: The Beginning is the first movie based on the anime series. It pretty much retells the basic story of season one, but with a different plot. Also, the relationships are somewhat different. Then there are the product placements.

The premise is that corporate sponsored superheroes compete on live TV for points awarded for arresting criminals and saving lives. Kotetsu, aka Wild Tiger, is the veteran of the group, who has lost a step or two over the years. Anyway, all that competition leads to some strained relationships which sometimes interferes with the business of enforcing justice -- which wasn't part of the original series.

In comes Barnaby, whom Kotetsu refers to as Bunny, whose powers are the same as Kotetsu, who really has a problem getting along with everyone, especially Wild Tiger. Mainly this is because he is forced to partner up with Wild Tiger.

Of the series and the movie, I prefer the series. The series takes time to develop the personalities of the supporting cast, and to provide more details on backstories. But the movie version is pretty good. My recommendation though is to watch the series.