Those having grandparents and parents whom lived thru WWII in,
either, the-then Malaya or Singapore, one would surely hear the
horrors of daily life during the japanese occupation. But I suspect
they did not really want to describe the full details as it is
still painful for them after so many years. Something most of us
can understand.
Popular bookshop does carry books on the japanese occupation. Or
else you can try the libraries. Researching this is never easy.
Won't be given to you in a silver platter. Try to piece the story
together depending on which aspect you want to concentrate on. The
entire subject of japanese occupation is too huge even for a PhD
thesis!
But from experience, the more you read into it, the more you get
drawn in. I have to admit, after reading books on the subject out
of interest, I have a deep hidden sense of hate towards the
japanese.