Is there any official report from Oricon?
EDIT #1:
Here it is: 現役大学生miwa、平成生まれのソロ歌手初の1stアルバム首位 (ｍｉｗａ) ニュース-ORICON STYLE- -
http://www.oricon.co.jp/news/rankmusic/86509/full/
EDIT #2:
I've been hearing from mellody that, as I predicted, she made history. But it was something that I did not even expect.
miwa was once again born on June 15, 1990, but there was something interesting that regards to miwa and the Heisei era:
in the history of the Oricon, miwa became the first-ever soloist born out of the Heisei era - any gender - on a debut album.
Now this is something that is really quite historic. Not only she joins the greats such as Ayu, Mika Nakashima and ayaka on getting a #1 on their debut album, but she becomes the first ever Heisei-era-born soloist to get a #1 on it.
NOTE: ayaka was born on 1987; the Heisei era started in 1989.