I have not been to Japan yet, but I plan on going some day.
One thing that I have always wondered about was how Japanese view foreigners, and by "foreigner" I mean more specifically half-Japanese foreigners because I am half-Japanese.
So if someone who has been there in recent years or knows someone who has been there in recent years could shed light on the topic I would greatly appreciate it!!
This matters where you go quite a bit. How foreigners are seen in Tokyo is very different than how they're seen in Kyoto or Hokkaido, or Osaka... etc. Even within regions what part you're in will treat you very differently. Atsugi which is very rural will treat you more respectfully and more patiently and less of "a tourist" than they will in Shibuya and Shinjuku. But if you go to more country areas like Fukui, prepare to be treated like utter trash because Japanese xenophobia is definitely not just a stereotype.
In bigger cities, you're treated as a tourist. What I mean is, they will pretend to be nice to you(and I really mean pretend) because you are giving them money, and you are getting the hell out of the country. There's a very big difference between people that are obviously tourist, and someone who is foreign living in Japan, and how they are treated is again, worlds apart.
You don't need to know the language at all if you're staying in Tokyo/Kyoto. These cities are very foreign friendly, and 90% of signs will be in English+JP. If you go outside of the main areas though, then knowing a little bit of JP is great, but having something to show people is even better. Having a map and/or printout to show someone will be the best way to get directions if you're lost, because even with very basic comprehension of the language, directions are confusing unless you have a pretty decent grasp of how language is. Also, City streets aren't so straight forward in Japan. The US works on a very gridlike map system, Japan doesn't at all. So streets curve a lot and angle every where. Again though, it's not difficult, and train stations are almost everywhere. A lot of people in train stations will be able to help you, and there is almost always at least 1 worker conveniently near you whose English is more than enough to communicate with you.
As a half-JP(What's your other half if you don't mind me asking) you are kind of at a disadvantage because happas aren't really well received in a lot of places. Again though "tourist" takes priority, but there will be some people that will blatantly show their racism to you.
Something useful, despite this, the JP are usually really meek to foreigners even if they don't like them. You can get away with all kinds of shit. Just scream a lot of English words and people will be scared of you.