Dive (Kano, Shiuko)

Onizawa is a detective who recently got a divorce. One of his colleagues, Honda, is murdered in what seems to be linked to other detectives that have been murdered. Yashiro is another detective that Onizawa has taken an interest in, but also seems to have had a close relationship with Honda in some way. Because of how young he is though how did he know Honda and can Onizawa get closer to Yashiro who strongly dislikes him?
(Source: MU)