Im diving into one of these Sony micro-tvs. Where are the high voltage tubes located? are they in the sealed box that contains the flyback?

Yes, that's correct.

and the box is sealed. not a very serviceable design

The original idea was to replace the
can with a replacement from Sony if there was a problem.

Yes, the Sony micro tv’s hid the rectifiers. Components on the boards are really close together. You had to have patience when working on these small sets. But what a novelty they were for there time. A solid state set when everything else in its time was tube and much larger. I always liked the style they had, but not so fun to service. I would recommend doing a total electrolytic replacement. The Elna caps weren’t the best and by now they would be leakers.

Shango did a video on small Sony's a couple of weeks ago.
He worked on the small TV4 set though also will be working on the identical set to yours.
https://youtu.be/JU0mo3TF07k
The small ones are even harder to
try to fix.

I picked up 4 of these. I got 2 of the earlier vhf only sets as well. One has a known bad crt, so it probably will be a parts set as among the 4 i bought, i have a crushed antenna, a missing channel knob, etc.

I think investing in a vacum desoldering gun, a magnifier, and some kind of fixture to hold the boards would be wise.

I'd recap it and confirm there's no HV before worrying about the tubes. The HV rectifiers in these early SS Sonys tend to be fairly reliable.
They are not socketed tubes (they are hardwired hearing aid style sub-minature types) so few testers have settings or provisions for checking them.

The symptom of a bad eht rectifier
is picture ballooning when you turn
the brightness up.
If you have several of them
trying another eht can is a fairly
easy option.