Kaitatsu (懐達) is an expression exclusive to the kingdom of Kei. The term literally means "to miss Tatsu" or "to pine for Tatsu." Tatsu (達) refers to the most recent male ruler of Kei, whose reign lasted for three hundred years. Though he inflicted great hardship upon his people at the end of his reign, he is remembered for governing wisely and peacefully throughout the majority of his rule.
However, after Tatsu's death, he was succeeded by a series of female rulers, all with extremely short reigns. The first of the three, Haku-ou (薄王), ruled for only sixteen years, and was known for her indulging herself in the luxury of being king and failed to govern. Her successor, Hi-ou (比王) managed twenty-three years on the throne, but quickly became corrupted by power and became tyrannical. The third female ruler, Youko Nakajima's immediate predecessor You-ou (予王), had held the shortest reign of all at six years, exhibiting qualities of neither of her predecessors and remaining withdrawn until her last days, when she emerged as a tyrant. The legacy of her predecessors is particularly daunting for Youko, who is the fourth legitimate female monarch for Kei after Tatsu.
After three female rulers with interregnums longer than their reigns and female pretender to the throne, the people of Kei have become suspicious of female monarchs and use the term kaitatsu to express how they miss a male ruler.