I know a person, who is my friend, named Yuuto and he uses the kanji 勇人. It is from 勇 (yuu) meaning "courage" and 人 (to) meaning "person". I would say this is the most common spelling of Yuuto in Japan. Also most of the bearers of this name use the kanji. (https://ja.wikipedia.org/wiki/%E5%8B%87%E4%BA%BA this includes a list of bearers who uses this kanji). [noted -ed]