Friends do take baths together in Japan. But yeah one of them does like the other romantically.
Yasumi mentioned that it's only normal for friends to bathe together at public baths and stuff like that. Getting in same the bathtub together
at home is a different matter. The difference should be obvious when you consider the size of a bathtub compared to a public bath or onsen! Some Japanese women still might have the sort of boundaries with their female friends where getting in a small bathtub together is okay... But what matters is that Yasumi sees this as outside her normal boundaries.
Never mind the fact that these two are desperate to deny that they're friends or "close". If they were literally just actual best friends, the bathtub incident would have been
less weird. They are coworkers who drive each other crazy, fight all the time, but can't leave each other alone. That's such a textbook case of romantic and sexual tension it feels silly to have to point it out.
