Isn’t it not good to have milk in somewhere hot? Or is this a Japanese thing?
Depends on several things, really. The method of sterilization, the water temperature, the milk temperature, how soon you drink it etc. But 'drinking cold milk after bath' is Japanese thing. 'drinking milk in bath', on the other hand, was never a thing; if you spilled some of it you'd need to drain the whole bath to prevent the stench sticking in the rocks.
