Tokkofuku means "special attack clothing" and was the uniform of biker gangs in Japan called Bosozoku ("reckless biking group").
It could consist of a long coat, boilersuit, toraichi pants, surgical mask to conceal identity, and boots or jika tabi. (As an aside, pairing toraichi and jika tabi is also popular with Japanese construction workers.)
Over the years tokkofuku became more elaborate with embroidered slogans, poetry, jokes, imagery, etc.
Wearing them can get you into legal trouble due to their association with criminal gangs. Their popularity peaked in the 1980s, but police pressure has all but eradicated bosozoku in recent times.
Despite the legal risks, the style has been adopted by fans of musical groups like AKB48 to express their fandom.
Bosozoku were popularly depicted in the anime Akira, with rival gangs the Capsules and Clowns.
Here are a few more examples of tokkofuku:
