I am looking for the top 1000 names in the Japan. Ideally I need this
information for people aged 12-25, but even if you just got the
statistics for kids born in a recent year (IE year 2000), this would suffice.

I need to know the following information for each name: 
1) how many people in the data set have this name. 
2) male or female name

I also need to know the total size of the data set.

For instance the results might look something like this:

There are 1 million kids born in the UK in the year 2000. Here they are:
1) Aiko - 80,000. female
2) Hiro - 75,000 male
...
1000) Emiko - 34 female