Haku

An amnesiac found wandering in the mountains in a hospital gown, he is found and nursed back to health by Kuon, and subsequently taken care of by her when she finds that he is physically extremely weak by demi-human standards, being unable to perform simple tasks that even children are able to do easily.

He is however clever and quick on his mind. He has shown being able to solve situations by thinking thoroughly about it.

After arriving in the capital of Yamato, he starts working at various jobs, at Kuon's demand. He is asked several times by Ukon to do missions for him, including reporting suspicious events and finding proof of someone's corruption.

(Source: Wikipedia)