The "Keiji Shichinin" drama series began in 2015 and Part 2 was shown last year. At the end of the last season, Katagiri Masatoshi (Yoshida), the chief of the general affairs section, declared the disbanding of the Betsudou Sousatai even though he did mention that there is a big job waiting for the 7 of them. This time, with the increase in criminal activity in the Tokyo Waterfront area, Katagiri becomes the chief of the Juuichi Houmen Honbu Junbishitsu to lead everyone in resolving cases from this area which is becoming the new battleground for people interested in the gains that come with the area's development before 2020. In addition, the truth behind the deaths of Amagi's (Higashiyama) wife and daughter 12 years in the waterfront area will also come to light in the sequel.
As for the atmosphere on the set, Takashima said that they are doing so well together that it is likely that they may do more sequels in time to come. Likewise, Kurashina commented that it's been 3 years since they came together for this series so they have become close enough. Tsukamoto who joined the series from Part 2, revealed that it's been so hot during the filming that he plans to bring some ice-cream as refreshments for everyone.
Sources: My Navi News / Oricon