Yutaro (sometimes spelled Yutarou) was at the beginning a very spoiled
boy who had no parents. He was looking for a swordsman to teach him
so he could become as good as his deceased father. But the only teacher
he had was just using him. In result of that, his right arm became useless
after his teacher struck him.

He got along with Yahico (sorta) and liked to argue with him. I think
they're relationship comes closer to being brothers than being friends.
Yutaro left for Germany to get his arm healed and then returned to
Japan with Dr. Hans. He decided to become a doctor instead of a
swordsman, and he was very good at it at his age.

I really did liked Yutaro. He was pretty smart. It showed when they were
on the quest for the miraculous medicine.