Four teenage boys were arrested earlier this month for allegedly robbing and injuring a man on a Tokyo street because they needed cash to buy custom-made outfits to sport in a handshaking event involving the pop idol group AKB48, police said Monday.

The boys, all from Saitama Prefecture, approached the victim, a 27-year-old graduate student, in Kita Ward on Aug. 11, grabbed him by the shoulder and demanded cash.

The youths fled the scene with the man's mobile phone and other belongings, slightly injuring the victim in the process.