Odds and Ends
Respect your elders
9 5, 3:46pm
Japan has kind of odd criminal justice system and it mostly dripples down to the over 99% conviction rate (over 99% of people brought to trial are convicted for the crime) and there's huge pressures for judges from their office to make "the right ruling" (meaning the ruling the office wants).
Also what I have heard Japanese police isn't a friend of suspects, there's rumours of interrogations spanning multiple days including stuff that could be in some light seen as torture (denying food and water, extreme psychological pressure, even physical violense) to get a confession because every other evidence is insignificant in Japanese crime investigation if the suspect confesses. But as said, those are rumours, no one really knows because suspect interrogations in Japan are done with closed doors and without attourneys.
Japan is trying to change things, but they have a very long way to go. They made it "mandatory" to video record interrogations and in 2018 81.9% of interrogations were filmed because there's two cases where the interrogations aren't filmed: when the suspect refuses to be filmed and when the interrogators think that filming would deter suspect from confessing.
So in some way it's not really surprising that there isn't unsolved homicide cases in Japan, but I would doubt that quite many homicide cases aren't as solved as they could be.