If you don't want to sightsee why don't you find a Ryokan (Traditional hotel) near an Onsen (hotspring) and chill out there for a few days?

When I say the only must do is Disney sea, I kinda meant like on top of the traditional sites you’d go to in these places

Still want to go to like Shibuya, Shinjuku, the typical stuff as well. I just haven’t really dug into it that much and I’ve never been anywhere in Asia before, but I definitely am interested in all the typical tourist sites

Osaka and Tokyo are super similar on the grand scheme of things. I think if you're spending a lot of time in Tokyo, you can skip Osaka unless there is something specific there you really want to see.

I'd add Kyoto into the itinerary. Spend a night there in a traditional ryokan. I can suggest the one I stayed at, I loved it. It's very much a tourist-thing to do.

Look up a town called Hakone, it's near Tokyo, at the base of Mt Fuji and is famous for its hot springs.

Outside of Tokyo, my next favourite place in Japan is Hiroshima. It's a bit further but super quick/cheap to get to. You can take the bullet train but I'd actually recommend a domestic flight from HND. Tourists can sometimes get special promotional airfares.