
Hmmm. Why isn't she wearing a bra in work though!? Is that a thing in Japan?

Hell, if my boobs looked so perfect under clothes, I wouldn't wear a bra either. But I think, that she IS wearing one. In the panel, where she initially starts taking off her top, there is a strip of lighter fabric that could be the already unhooked bra, since her top doesn't have that lighter fabric at the bottom.
That's a really long tag.
And I often do that too