Japan's lack of the word apology is a cultural thing...
Toward the end of the Occupation of Japan, Emperor Hirohito let it be known to SCAP that he was prepared to apologize formally to Gen. MacArthur for Japan's actions during World War II—including an apology for the December 7, 1941 attack on Pearl Harbor.
Patrick Lennox Tierney was an eye-witness on the day the Emperor came to SCAP headquarters to present this apology. When the emperor arrived, MacArthur refused to admit him or acknowledge him. When this happened, Tierney was in his office on the fifth floor of the Dai-Ichi Insurance Building in Tokyo. This was the same floor where MacArthur's suite was situated.
The pivotal moment passed. Many years later, Tierney made an effort to explain his understanding of the significance of what he had personally witnessed: "Apology is a very important thing in Japan." Issues which might have been addressed were allowed to remain open, and unanticipated consequences have unfolded across the decades since then.
1957. Prime Minister Kishi Nobusuke. "We view with deep regret the vexation we caused to the people of Burma in the war just passed. In a desire to atone, if only partially, for the pain suffered, Japan is prepared to meet fully and with goodwill its obligations for war reparations. The Japan of today is not the Japan of the past, but, as its Constitution indicates, is a peace-loving nation."
Also in 1957. Prime Minister Kishi Nobusuke. "It is my official duty, and my personal desire, to express to you and through you to the people of Australia, our heartfelt sorrow for what occurred in the war."
September 29, 1972. Prime Minister Kakuei Tanaka. "The Japanese side is keenly conscious of the responsibility for the serious damage that Japan caused in the past to the Chinese people through war, and deeply reproaches itself. Further, the Japanese side reaffirms its position that it intends to realize the normalization of relations between the two countries from the stand of fully understanding 'the three principles for the restoration of relations' put forward by the Government of the People's Republic of China. The Chinese side expresses its welcome for this" (Joint Communique of the Government of Japan and the Government of the People's Republic of China).
As you can see, the word apology doesn't appear anywhere officially, but that would change in the 90s...
July 6, 1992. Chief Cabinet Secretary Koichi Kato. "The Government again would like to express its sincere apology and remorse to all those who have suffered indescribable hardship as so-called 'wartime comfort women,' irrespective of their nationality or place of birth. With profound remorse and determination that such a mistake must never be repeated, Japan will maintain its stance as a pacifist nation and will endeavor to build up new future-oriented relations with the Republic of Korea and with other countries and regions in Asia. As I listen to many people, I feel truly grieved for this issue. By listening to the opinions of people from various directions, I would like to consider sincerely in what way we can express our feelings to those who suffered such hardship"
August 4, 1993. Chief Cabinet Secretary Yōhei Kōno. "Undeniably, this was an act, with the involvement of the military authorities of the day, that severely injured the honor and dignity of many women. The Government of Japan would like to take this opportunity once again to extend its sincere apologies and remorse to all those, irrespective of place of origin, who suffered immeasurable pain and incurable physical and psychological wounds as comfort women"
But these were all directed to the women forced into sex slavery, not to the nations for the invasion thereof. Then, finally on August 23, 1993...
Prime Minister Morihiro Hosokawa. "After 48 years from then, our nation has become one of nations that enjoy prosperity and peace. We must not forget that it is founded on the ultimate sacrifices in the last war, and a product of the achievements of the people of the previous generations. We would like to take this opportunity to clearly express our remorse for the past and a new determination to the world. Firstly at this occasion, we would like to express our deep remorse and apology for the fact that invasion and colonial rule by our nation in the past brought to bear great sufferings and sorrow upon many people" (Speech at 127th National Diet Session).
And again on September 24, 1993. Prime Minister Morihiro Hosokawa. "I used the expression war of aggression and act of aggression to express honestly my recognition which is the same as the one that the act of our nation in the past brought to bear unbearable sufferings and sorrow upon many people, and to express once again deep remorse and apology" (128th National Diet Session).
Diet has never officially used the word apology in any resolution, but it finally issued a statement that expressed it's remorse in June 9, 1995. House of Representatives, National Diet of Japan. "On the occasion of the 50th anniversary of the end of World War II, this House offers its sincere condolences to those who fell in action and victims of wars and similar actions all over the world. Solemnly reflecting upon many instances of colonial rule and acts of aggression in the modern history of the world, and recognizing that Japan carried out those acts in the past, inflicting pain and suffering upon the peoples of other countries, especially in Asia, the Members of this House express a sense of deep remorse"
Unfortunately that is about all you will ever get from Diet. But it should be pointed out that when an Emperor says something, Japan views it as being said for *all* of Japan, and when the Prime Minister speaks, his words are the words of the government of Japan, or so they view it. When one of these top officials say I, all of Japan is saying I with them. And it is so hard for the Japanese people to say "sorry" or offer an apology in their culture that they say they are remorseful or filled with remorse.
Will we ever get a formal apology from Diet? I doubt it.
Does it matter? To some, yes. To others, no.