Couldn’t they get him an electronic one at least?
A good, 88-key electronic piano costs several hundreds of dollars, if not thousands. Even an acceptable device with a reduced range will cost a few hundred dollars. And this boy probably won't stick with it.
(In America, old-fashioned upright pianos can often be purchased for far less that good electronic devices. I don't know whether this situation obtains in Japan. In any case, the cost of having it tuned would still remain, and the home might not accommodate a piano.)
The intelligent thing, if a child expresses interest and if the parent can afford them, is to get the child some introductory lessons. If he or she shows promise and commitment, then getting an instrument might make sense.