I was also thinking that if I "miss" my flight, I can go to the counter and tell them to book me on the flight the following day for no extra charge
Thats a pretty big chance you're taking, depending on how you're ticketed and the agent you meet, you might end up paying more (reticketing fees etc etc).
From my point of view its safer and cheaper to either have your friend meet you at Narita Airport, or have it shipped via delivery service is pretty safe and I personally never had a problem with, there's also a post office in Narita Airport if you want to ship the items that way.