Japan lost thousands of its own citizens during the Second World War. It was the dropping of the two atomic bombs that forced it to surrender. Now it was forced to apologies for the atrocities it committed. No war is 'holy" and wars are not fought according to "rules of the book". Everything is fair. Wars result in brutalities from BOTH sides. What difference an apology would mean now for what took place during the Second World War? It means nothing. Most of those who suffered are no longer around. The same holds to true for the atomic bombings of Hiroshima and Nagasaki where hundreds of thousands perished within seconds of the attack and those who survived, just wished they hadn't. Will a simple "We are sorry" after so many decades of the attack mitigate the pain and sufferings of the victims?
The scars of brutality always remain, and that is what history talks about -- the glorifying, courageous acts of the victor as they become writers of history, and the cruel deeds of the vanquished.