17, first time in Japan with my mom, very unprepared, desperately need help

Hi, I hardly use Reddit but I'm in dire need of some help.

My mom booked a trip for her and I next month, except she expects me to figure a lot of it out. Except I've never been to Japan, we don't go on international trips often (in Europe it was constant bickering with my siblings), and I don't know the first thing about planning something this huge. I thought we were going next year with the whole family, but she dropped this on me suddenly. I didn't even ask to go, but it looks like we are.

The trip itself is 9 days. We're flying into Narita and she wants to stay in Tokyo for 3 days then elsewhere for the rest of the time. I don't even think she knows where she wants to stay for the following few days. I've never booked a hotel. I have no idea where to go. I have lots of questions.

First, we're taking the train from Narita to Tokyo. The hotel I'm looking at is in Shibuya, which I guess we can take another train to. I think I can figure out Tokyo with some more help. Is there anything super special to check out while we're there? Or is roaming and finding things ourselves the way to go?

For the rest of the time, it's balls in the air. My mom expects to take public transit the whole time, so I guess wherever we go has to be accessible like that. She just wants to see nice attractions, which I understand, but also have no clue as to what she means. What can we go see that's tourist and beginner friendly? Does anyone have recommendations of areas to stay the rest of the time?

I also need general culture advice. Literally any at all. I'll do more research online, but this is the baseline.

Please no sarcastic comments. Reddit's asking me to add a flair but I'd put all of them down if I could. This is insanity. I'm dying out here.