Nationality Japanese

Check his appearances in Memories 2.

Check his appearances in J Boys challenge.

There is the kanji for "one" in his first name and he's first born, just like there is the kanji for "two" in the first name of the second son Eiji, and the kanji for "three" in Genzo, who is the third son, which is obviously a pun, making them 1st, 2nd and 3rd born of the family.