A Passionate Heart (1990)

Detective Ooki is investigating the murder of the head of the Shimoda clan, and the disappearance of his best friend, Detective Kobori. Miyata, the president of the Monma clan, who was in a war with the Shimoda clan, is arrested as a suspect, but he denies the charges. Just as the case seems to be going on for a long time, information comes to light that the Shimoda clan is smuggling drugs from Thailand, and that the boy who was carrying the drugs and Iijima, the dead leader of the clan, had a gay relationship. Furthermore, the fact that Kobori had been in contact with the boy comes to light. Ohki, who believes that the key to the case lies in Thailand, heads for Thailand.