The unsolved 1987 murder of an Asahi Shimbun reporter at the newspaper's Hanshin bureau had just one year as of Thursday before the 15-year statute of limitations runs out.
And investigators are no closer to an arrest.
Over the past two years, a Hyogo Prefectural Police task force questioned about 20 people linked to rightist groups for information that may relate to the case. The number of task force members has meanwhile been reduced from 120 at its peak to about 30.
"We will do our utmost until the very final moment to resolve the case," Akinori Tsuruya, director of the Hyogo force's criminal investigation division, said Thursday while attending an anniversary memorial held for reporter Tomohiro Kojiri at the daily's bureau in Nishinomiya, Hyogo Prefecture.