The Japanese still raped and pillaged Nanjing/Nanking to the extent that Little Boy was required. This is documented in history. There's a sugar coated film for the West about it.

If people want to see a gut-wrenching look at what happened in Nanking, sort of the equivalent of the Chinese version of Schindler's List, definitely check out the film The City of Life and Death from 2009.

It's long, absolutely horrific, and extremely brutal. Lots of rape and murder of women, kids and babies. Definitely one of those movies that will stick with you, much like the film Come and See (they're both very similar in tone, but The City of Life and Death is a lot more violent from start to finish).