What caused all these? Or triggered Japan to use suicide weapons? 

​Battle of Midway made Japanese question themselves, where they lost four carriers, a cruiser, and 292 aircraft, but in the second battle of Philippine Sea, they lost another three aircraft carriers and didn't do nearly as much damage to the U.S. Navy. ​
The Second Battle of the Philippine, June 1944, was another big loss for Japan, as mentioned above, it eventually led to Japan putting its hope on suicide weapons being able to stop the allies from invading Japan.
​
*The first picture (left) is a cartoon of a kaiten heading towards a U.S. ship, the picture on the right is several kaiten pilots standing on a kaiten on Japanese submarine I-361.
  • Hiroshi Kuroki - Co-inventor of Kaiten,  a rising star in the Japan Imperial Navy and a submariner.
  • Sekio Nishina - Another submariner that joined Kuroki in the petition, thought this would be a good idea to turn the tides of the War.
  • Yoshinori Kamibeppu -  Kaiten pilots, one of the four kaiten pilots aboard of submarine I-37, that was sunk during the Kikisuki mission. ​
*Sub-Lt. Sekio Nishina and Lt. Yoshinori Kamibeppu.
*First picture, left to right, are the four pilots of I-36, Imanishi, Toyozumi, Yoshimoto and Kudo. In the second picture, are kaiten pilots Sato, Nishina, Fukuda and Watanabe, of I-47. 
*Secret base of kaiten. 
Kaiten pilots were volunteers and many of them were officers that had graduated from “Etajima” the Japanese Naval Academy. While the Imperial Japanese Army treated recruits and even combat veterans harshly, this practice was rarely used within the Imperial Japanese Navy. They slept in western style beds and were well fed including delicacies that were scarce near the end of the war.
​