Japanese idol groups AKB48 and HKT48 held their concerts at Saitama Super Arena on 1 April 2018. During the concerts, AKB48 research studnet Inagaki Kaori and HKT48 member Akiyoshi Yuka accidentally fell off the stage and got injured.

After medical diagnosis, Inagaki Kaori fractured her occipital bone (located in the lower, back portion of skull); Akiyoshi Yuka fractured her ring toe and little toe bone.