"To ensure that the Yagyu-Shinkage School reigned supreme in the land as the Shogun's favored school, Lord Yagyu Tajima had seen to it that all of the other schools were politically eliminated one by one. His son Yagyu Jubei, however, had become a swordsman, against the wishes of Lord Tajima."
Yagyu Jubei became the greatest swordsman in Japan. One of the schools that had been driven to near extinction was the Ryujoji-Shinkage. One of the Ryujoji was the last to challenge Yagyu Jubei and failed. However Jubei was also near death. He called his disciple, Koinosuke, to his side and handed him a heart shaped eye patch which he called "the lovely-eye patch". He told Koinosuke to find someone with "plump plump, bouncy bouncy, bon bons" who would be the one worthy to inherit his legendary sword techniques.