Famitsu’s report from the event says the movie featured a young boy walking around Kamurocho in the rain. The publication believes the kid is the game’s protagonist. Text from the trailer explain the boy will commit crimes in the future and he is fated to fight.
The video closes with the line, “a new challenge for the Yakuza series begins.”
Further details such as release timing, platform(s), and who the boy is were not announced. Project K? Could the “K” stand for a young Kazuma Kiryu or the fictional (but based on a real world part of Shinjuku) Kamurocho?