In the early morning of the 4th, in an house in Kohoku Ward, Yokohama, a person dwelling in a room on the second flooring attacked a person dwelling on the primary flooring with one thing like an imitation sword and shut himself up in his room. Police secured the person at round 10:00 am, about eight hours after the report, and are investigating the main points.
Source
Yokohama A person who attacked a neighborhood man and injured him shut himself in his room for about 8 hours | NHK
