On January 18, 2014 at 10:30 pm, a man stabbed another man three times in the chest at a bar in the Amakubo area of Tsukuba. The victim died the following morning in the hospital. The perpetrator, who is described as being around 40 years old and wearing a beige jacket, left the knife in the bar and fled. He has not been found yet. Police are treating this as a homicide investigation.
Here is an article (in Japanese) about the stabbing
It seems that there may have been some history between the victim and the perpetrator, because according to the linked article, the perpetrator walked into the bar, immediately stabbed the victim, and then left, without harming any other people. In addition, the men were seen arguing in the street before the stabbing incident.
In any case, as the perpetrator is still at large, it is important to continue to take regular safety precautions.