Japan has several advantages as a nation. On the other hand, I believe there are some customs in Japan. For example, criminal justice systems in Japan is outdated.
In a historical point of view, Japan has strengthened the degree of punishment for crimes repeatedly. In recent years, a person who caused a traffic accident while recognizing that he or she had a risk, (e.g. some physical or mental diseases) was to be accused of "vehicular homicide." Thus, people who have epilepsy or diabetes are likely to be punished harshly when causing a car crash.
As well, the punishment for juvenile crimes is gradually enhanced.
It is well known that longer imprisonment is unlikely to prevent further crimes by the perpetrator. Also, it is doubtful to make other people stop committing crimes. At least in the level of academic research, harsh punishment is no longer useful for public safety at all.
In addition, imprisonment is costly. In Australia, 1,000 USD per year is needed for keeping a criminal in the prison. The situation is similar in Japan.
The Conversation: Mandatory minimum sentences and populist criminal justice policy do not work – here’s why
Also in Australia, dilation of the mandatory term of imprisonment seems to be a recent trend. The main reason may be the rise of populism. Excluding criminals from our society sounds good, because no one wants to be victimized.
However, it would not be a solution in a longitudinal view. People who were incarcerated will be released some day. If they have not learned the way to be reintegrated into the community, they will have no choice but re-offend. In real, longer imprisonment gets rid of the power of living from detainees.
In Japan, 90% of the people support the capital punishment. It is shameful to know my neighbors will never accept people with offending history. It represents the tradition in Japan not permitting a failure.