Board Thread:Questions and Answers/@comment-24487529-20150302230813/@comment-6697950-20150303223407

And my answer was based on the Japanese text. 小学校 and 中学校. According to wikipedia, 小学校 is up to 12 years old. But that's still just her estimate, so it can't be regarded as a reliable reference.

Anyway, my point is that we don't know how the restriction is enforced, we only know that it doesn't absolutely prevent any minors from using it. So, that's one part of your question answered and one possibility ruled out. However, the reason why the restriction is there in the first place isn't mentioned, so we don't have conclusive evidence if/how the NerveGear is considered to be unhealthy. Though since there is an age restriction and it's tied to the device rather than the game, there probably are considerations that it may not really be healthy for the younger audience.