By the time the Kaiten submarines and kamikaze tactics became a thing, Japan was in an absolutely hopeless situation. While the war was hopeless from the getgo, the military had deluded itself into thinking that they would be able to bleed the West into a negotiated treaty. While the actual thought behind their planning was a use of defense in depth, islands as unsinkable aircraft carriers, and an obsolete as well as poor understanding of American war planning, this sort of thing doesn't go over with the populace as talking about the so-called "Yamato-damashi," or the "Spirit of Yamato," emphasizing some sort of Japanese inherent superiority over other races.

The reason these tactics became popular was due almost entirely to the decimation of the Japanese air and naval arms in a war of attrition throughout 1942 to 1944. The elite corps of Japanese naval aviators-the pilots whom had been the terror of the Pacific for early 1942-had been bled dry, replaced by trainees piloting obsolete aircraft (the A6M2 Zero was simply outclassed by armored planes like US Hellcat fighters, the A6M5 Zero was outclassed by the contemporary Corsair, and the A7M Reppuu came too late in the war to actually do anything). This was seen during the battle of the Philippine Sea, where Japanese naval aviation suffered dreadful casualties while inflicting virtually no damage on increasingly veteran US pilots.

Japan's industry was also in no shape to develop any actual sophisticated weapons. Aside from being bombed to bits, Japan's industry had never even been remotely comparable to American industry from the get go. The one resource Japan had in relative abundance was manpower. Life was, essentially, cheap.

Young officers, inspired by the whole "Yamato-Damashi" rhetoric, sought to find and develop wonder weapons within Japan's means that could possibly turn the tide. The use of kamikaze tactics, for example, was a way for Japan to have an airborne anti-ship option that even green rookie pilots could use. Green rookie pilots would be chopped to pieces by superior US pilots if they tried to maintain attack runs on US ships, not to mention they would not have any aiming practice with their weaponry. On the other hand, steering a plane in a straight line against a ship is a relatively straight forward task. In a time when Japan was able to mobilize more manpower than they could train properly, it was a simple if brutal solution.

The case of the Kaiten was along this line as well. If I remember the story correctly, two young officers (who were friends) had the idea to develop these guided torpedoes. I also seem to recall a grand total of one of these torpedoes actually worked, and that was one of those two officers piloting the Kaiten (with his friend's ashes, who had died in a Kaiten accident).

Tameichi Hara remembered being commissioned as a teacher at a torpedo school, where many of the trainees were to pilot suicide PT boats or act as frogmen. Despite personal revulsion, he nonetheless ended up having some of these trainees preparing for suicide missions (that, he happily notes, most of them never had to execute).

There were cases of, for example, Chinese in the Sino-Japanese war, who, due to lack of heavy weaponry, were forced to rely on satchel charges and the like to deal with hard targets. There is more than one instance of Chinese troops essentially launching suicide attacks with satchel charges onto Japanese tanks and fortifications. In all cases, though, these suicide missions were not done out of some death cult idea of war as they were more out of sheer desperation.