Answer
The vowels present in the romanized version of Yoichiro's first name are A, E, I, O, and U. This is because the Japanese language has a rich vowel system, with five distinct vowels: /a/, /e/, /i/, /o/, and /u/. The romanized version of Yoichiro's first name retains all of these vowels, as they are essential to the pronunciation of the name.