Water, milk, fruits and vegetables in Japan

Is the water safe to drink?

Yes. Tourists don't have to worry about drinking the tap water in Japan It's perfectly safe. Their  drinking water is like the water in the United States or in Westen european countries. If you drink the tap water there, you can drink it in Japan. If you prefer bottled water in general, you can find that in Japan too. But you don't need to boil tap water or add tablets to purify it.

What about the milk?

That's quite all right too. The milk is pasteurized and safe to drink. Milk and milk products sold commercially are prepared under sanitary conditions. It's the same as in other advanced countries.

And the fruits and vegetables? 

The same as with milk and water - you don't have to boil or soak fruits or vegetables before using them. The standards of cleanliness are high. The risks of food contamination are about what they'd be in the States or Western Europe.