Ōendan

An ōendan (応援団^?), literally "cheering squad" or "cheering section", is a Japanese sports rallying team similar in purpose to a cheerleading squad in the United States, but relies more on making a lot of noise with taiko drums, blowing horns and other items, waving flags and banners, and yelling through plastic megaphones in support of their sports team than on acrobatic moves (though some ōendan incorporate pom-pom girls). In addition to cheering for their own teams, ōendan have been known to lead fans in cheers which tease and taunt the other team and its fans. This is usually done in the spirit of good competition, but occasional fights have broken out if the taunting gets too heated. Smaller ōendan are sometimes called ōenbu (応援部^?) (or "cheering clubs").

Ōendan or ōenbu can be found in high schools, colleges and universities, as well as in non-academic settings such as intercompany sports clubs, professional sports fan clubs, and so on. Many schools hold competitions during their sports day events, and students often spend weeks perfecting their presentations after being divided up into teams.

Many members of an ōendan will dress in long happi and wear hachimaki emblazoned with team logos, inspirational sayings, or the names of their favorite players, something adopted by some fans of Japanese idol groups.

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Wikipedia