Unaccompanied minor traveling to Tokyo and back to USA

Hello all,

I am traveling to Japan next Thursday as a unaccompanied minor.

I was wondering what to expect during customs and immigration in both Japan and the US.

I heard that for the US, I needed a notarized letter of consent for my parents, but I've also heard that it was just a recommendation and that you don't really need it. On the Japan side, I haven't really found much information about customs and immigration in Japan. I've already booked the hotels in Japan and got the necessary paperwork to stay in said hotels. I am a US citizen if that helps.

Thanks in advance!