Where is League of Legends Yasuo from?

Ionian ... The theme is a hero with Japanese kendo as the background.

Yasuo was once a talented apprentice in a famous fencing Dojo in Ionia. He was the only student of his peers who could master the legendary fencing. Most people once believed that he was destined to be a great hero. However, because of the invasion of Noxas, his fate was changed forever. Yasuo was in charge of protecting an Ionian elder at that time, but he thought his sword could change the situation, so he went AWOL and joined the battlefield. When he returned to the elder, he found that the elder had been killed.

From Baidu Encyclopedia: Yasuo