Re: Japanese names when used in English?
In the example given above, "Toshiro" would be the actor's first/given name and "Mifune" would be his last/surname.
In America and other English speaking countries, I introduce myself as "Jun Akiyama." I guess I would and have done that in other languages such as Spanish and German as well. In Japan, I would most likely introduce myself as "Akiyama Jun" ("Akiyama Jun to moushi masu").
When I talk about a Japanese person in English, how I refer to him/her depends on my relationship with that person. For example, my aikido instructor (who is Japanese) would be referred to by his last name and "sensei" (eg "Mifune sensei," if Toshiro Mifune were my aikido instructor) due to the fact that he is hierarchically above me in the aikido world. If I weren't doing aikido and he was just someone whom I knew but not familiarly, then I would probably refer to him in English as "Mr. Mifune" but in Japanese as "Mifune san." Only in contexts where there is no personal relationship (eg speaking of Toshiro Mifune the actor) or in instances where I might be implying some sort of equality (eg when speaking of someone else in my class level in school), familiarity, or even derision/condescencion would I just call someone by their last name (eg "Mifune"). About the only Japanese people whom I would personally feel comfortable referring to by their first name are those with whom I am familiar (eg family friends) or those who is at or "below" my relative hierarchical place in society (eg same age or younger).
This is just my experience...