The Japanese people were very, very patriotic. In addition, they firmly believed that the emperor was god on earth. He was a living god and whatever his decisions, they were from god himself. Between those beliefs and feelings, the opportunity to die for the preservation of the country was not even a question. They all knew that their country was in dire straits with a terrible enemy approaching their shores. As soldiers in the service of their living god, they were much more than willing to sacrifice their lives to save their country.
There were several aspects to this belief. A deeply ingrained concept of Yamato-damashii (大和魂, “Japanese spirit”) or Yamato-gokoro (大和心, “Japanese heart/mind”) was implanted in every Japanese clear back to the Heian_period (794-1185 AD). Ironically, it might be noted that “Heian” means “peace” in Japanese. This concept was that Japanese spirit and values were far superior to the spirit and values of any other culture. Yamato-damashii embodied the concepts of the Japanese being brave, daring, and having an indomitable spirit. So, each and every Japanese was imbued with the basic concepts necessary for them to know that they were better and superior to all other peoples.
Another principle of Japanese doctrine was Hakkō_ichiu(八紘一宇) which was that the Japanese people, being superior to all others, were destined to rule. Hakkō ichiu, literally “eight crown cords, one roof” (i.e. “all the world under one roof”) meant that the Emperor of Japan was to rule an empire, not of just the islands, but also many conquered lands. Consequently, not just the people, but the military had the concept that whomever they conquered deserved it. They should be happy to have become a part of the enlightened ones even though the Japanese felt that all other peoples were lower than dogs.
Gyokusai was a Japanese philosophy has been expressed as, “Better to be a shattered jewel than a roofing tile.” The Gyokusai ideology reached its peak during WWII and was expressed in action, as honorable death (ichioku gyokusai, ie, shattering jewels into a million pieces) in combat was far preferable to living as a prisoner. This philosophy is outside Bushido or any religion and was part of the Japanese psyche applying to soldiers and civilians alike. What is Gyokusai? 玉砕とは何でしょう? The Japanese Army regularly chanted the mantra, “Whether I float as a corpse in the waters or sink beneath the grasses of the mountainside I willingly die for the emperor,” and concluded “The life of a warrior is like a cherry blossom which lasts but three days.” There were many slogans but towards the end of the war one of them was, “One plane for one battleship. One boat for one ship. One man for one tank or ten men.” Another slogan to indoctrinate the warrior spirit was, “Duty is weightier than a mountain, but death is lighter than a feather.”
An example of the Japanese military mind was evident as early as the morning of December 7, 1941. Ensign Kazuo Sakamaki, who was captured unconscious when his submarine ran aground after the attack on Pearl Harbor requested to be shot or allowed to commit suicide. He became Prisoner of War #1. On the other side of Oahu, A Japanese D3A1 Carrier Bomber was shot down by a P-40 and the two members of the crew bailed out off shore. One died, but Petty Officer Goto made it to shore and was seen. A team from the 55th Coast Artillery approached him and demanded his surrender to which he replied with his pistols. Goto had recovered a pistol from the body of his other crew member and now, 4000 miles from Japan, all alone, with no food, water, or possible reinforcement, he fought to the death rather than surrender. Over Honolulu, as the attack of the second wave ended, 28-year-old Lieutenant Fusata Iida, commander of the Japanese 1st Shotai from the Soryu, found that his Zero was too badly damaged to make it back to the carrier, so he dove to his death in a Kamikaze dive crashing between the hangers at Kaneohe airfield.
So the reason was that they felt that they were sacrificing their lives in order to save their country.
– Frank Duncan