In Japan the power of the Yakuza was drastically weakened, partly because the sorts of people it would typically recruit were instead joining the armed forces, but also due to increased anti-subversive and anti-dissent activity (which by its very nature would hurt the Yakuza).

Ironically, after the war, due to the collapse of the old Japanese system, and the influx of thousands of soldiers and secret policemen seeking to avoid trial for war crimes, the Yakuza swelled in manpower and strength, at least enough so to actively influence the Japanese government on multiple occasions in the post-war era, prior to the 1990s crackdown.

Sweden, while neutral, experienced a wide-spread increase in crime rates during ww2.

Here's a diagram showing a peak in severe crimes during ww1 and ww2.

It has been speculated that the increased social and physical movement during the wars, the blackouts, the rationing and hard times led to a higher crime rate during the war years.

There was a SIGNIFICANT rise in crime during the London blackouts. The official figures show that the amount of recorded crime rose by nearly 60%

The cover of the black out and the opportunity to loot damaged properties were not the only reasons.

Adults with less than 3 months to serve and juveniles with less than 6 months to serve were automatically released early from prison or borstal, because of necessary cut backs to the prison service. The police force was also cut back for similar reasons.

Add to this the increased demand for black market goods because of rationing and there was the perfect mix of increased opportunity and decreased chances of getting caught and serving a long sentence.

As a follow up question, was there an increase post war once the men returned home?

Thanks for the answers everyone!

Late post here, but I found an article relevant to your question in a Nov. 2, 1914 dispatch from the Associated Press. (Bottom-right corner.)