Seven years of cycling in Japan...
Tokubin and other delivery services are available just outside of baggage claim at Narita. Probably a 3000 yen charge for next day delivery. Offer to have your friend meet you at Narita by train - easier for everybody.
Just get on your bike and ride. Police will avoid you and nobody will care that your bike isn't registered. Make sure you lock it though, because borrowing bicycles is sorta not considered a big deal in Japan. Also lock it where there are other bikes, not just "barra barra". The borrowers will take the ones that aren't locked.
As far as routes go, stay off the highways and just follow your nose. If you can't read kanji, then maps are useless. My guess is that after a while you'll start using local trains like everyone else.