TOKYO—It was a slow Wednesday night at an Osaka club called "Noon," and the DJ was playing Suede's 1996 single "Trash" to a crowd of about 20 people. Suddenly, at around 9:43 p.m., a police force twice that size barged into the club and took staff into custody.

Club owner Masatoshi Kanemitsu rushed to the scene and was arrested too. He said he spent 22 days in detention after the 2012 incident, undergoing constant interrogation. Osaka police declined to comment on Mr. Kanemitsu but said it is normal practice...