After the mysterious death of robotics genius Hayato Kano, Mizuki and their only daughter Sayoko fled to England. There, Sayoko quickly caught the attention of the Ministry of Defense when she created a small robotic toy from everyday parts found at home and without her mothers knowledge, brought it to school. Later on she would create the MMP and SAM which soon gave birth to Behemoth, UK's first combat mecha. Japan quickly recognizing Hayato Kano's work and ripped through his government lab and found, locked deep within his files, detailed plans of a smaller version of SAM which he used to implant all of his knowledge into his daughter Sayoko's brain.
Once the UK entered the scene with Behemoth, Japan quickly recognized Hayato Kano's craftsmanship. After ransacking his office and discovering he had implanted his most vital mech design specs in the mind of his daughter Sayoko, the Japanese military stole what files remained and attempted to make a combat mech of their own. Unfortunately after months of failed attempts, Japan was still unable to develop an internal power core strong enough to with stand any type of sustained combat without over heating and shutting down. No matter how much they tried they were unable to get around Kano's fail safe cool down devices. Taicrom was to be Japan's symbol to the world that they are once again ready to enter and be recognized as a super power, but not until they could have an effective war fighting machine.
The Japanese government immediately started to put pressure on England to deport Mizuki and Sayoko realizing that Sayoko was their only hope. Tensions mounted when England refused to deport Mizuki and Sayoko back to Japan. England finally gave in but not until Sayoko produced design plans for 2 new combat mecha that the UK immediately began work on.
Once Sayoko was back in Japan, the government wasted no time in having her design their very own combat mecha, and within months Raijin was born.