A seemingly cold and emotionless man of Masayuman descent, Hideyaki left his homeland and traveled the world to perfect his swordsmanship. After learning all he could about the Masayuman method of swordsmanship, he visited the sword schools of the Ling Zhao, then studied the methods of the dervishes of Al'Kazmeer, Thalian air sailors, and Sturmgaardian paladins. He even managed to get some elves to teach him a bit of their own graceful ways of the blade, incorporating everything he learned into his own unique sword school.
Rather than returning to his homeland after his travels, he settled in Alestia and opened a school there. It became a school of renown, and the Electors greatly desired that he teach his techniques to the Alestian military. While Hideaki refused, wishing to keep his school separate from any governmental body or other powerful organization (part of the reason he did not return to Masayume), he was willing to teach a select few elite, such as the Royal Guard tasked with protecting the Prince/Princess and the Electoral building. Part of the school's prestige comes from the fact that he is a manifest, and as such is better suited to teaching those few who share his magical abilities. However, the majority of his students are mundane, but even if they don't have eminence, they still have much they can learn from Master Arima.
Though he looks to be a Masayuman man with a shaved head in his mid 40s, Hideyaki moves with the speed and strength of a young man in their prime, while his eyes seem to possess the wisdom and experience of someone much older.