Thread:Hatsu39/@comment-25832576-20150614210024/@comment-140.112.5.4-20150704062459

39 (as "three nine" instead of "thirty-nine") reads "Miku" in Japanese, and there's a very famous VOCALOID character called Hatsune Miku.

So it's no wonder such a name would appear in a music game as an ID.

Actually, I think it's possible that THIS Hatsu39 here was named after the exact same character, too, wasn't it?