 Stop ! ! Hibari @-@ kun ! follows Kōsaku Sakamoto , a high school student whose mother tells him on her deathbed to live with her friend and yakuza boss Ibari Ōzora and his family in Tokyo after she dies . Although Kōsaku is initially unsure about his situation , he is relieved when he meets Ibari 's four children : Tsugumi , Tsubame , Hibari and Suzume . Kōsaku is attracted to Hibari from the start , but he is shocked to learn that Hibari , who looks and behaves as a girl , was assigned male at birth — something only known within the Ōzora Group and Hibari 's family . A group of four girls led by Kaori <unk> begin to suspect that Hibari may be a guy , but Tsubame takes Hibari 's place during a health <unk> , effectively <unk> any suspicions . Hibari begins to show an immediate interest in Kōsaku , so in an effort to distance himself from Hibari , Kōsaku joins the Wakaba Academy boxing club . Also in the club is Makoto Shiina , who is attracted to Hibari , and Rie Kawai , the club manager who Kōsaku likes . Hibari soon joins the club as its second manager shortly before they go on a training camp in <unk> at the end of the year . 
