[Corvina]

Hikki's "Can You Keep A Secret?" got Platinum as full song in September, so I just made the list for her.

Hikaru Utada

Spoiler:

Chaku Uta (ringtone, just parts of songs)

2 Million
Flavor Of Life -Ballad Version-

Million
Flavor Of Life
Prisoner Of Love

Triple Platinum
Keep Tryin’
Double Platinum
Easy Breezy
Be My Last
This Is Love
Beautiful World
Kiss & Cry
Stay Gold
Dare ka no negai ga kanau koro

Chaku Uta full (or Single track/ full songs)

Million
Prisoner Of Love
Flavor Of Life
Beautiful World

Triple Platinum
Flavor Of Life -Ballad Version-

Platinum
HEART STATION
First Love
This Is Love
Can You Keep A Secret?

Gold
Keep Tryin’
Boku wa Kuma
Passion
Be My Last
Kiss & Cry
Fly Me To The Moon (In Other Words) -2007 MIX-
Stay Gold
Hikari
Eternally -Drama Mix-
Eternally
COLORS
Come Back To Me
Beautiful World -PLANiTb Acoustica Mix-
Automatic
Dare ka no negai ga kanau koro
Can't Wait 'Til Christmas
Goodbye Happiness
SAKURA Drops

PC

Platinum
Flavor Of Life
Beautiful World
Sakura Nagashi

Gold
Goodbye Happiness
Can't Wait 'Til Christmas
Kiss & Cry
Keep Tryin’
This Is Love
Flavor Of Life -Ballad Version-
Prisoner Of Love
HEART STATION
Eternally -Drama mix

That’s 49 certifications with roughly 16,5 million downloads.

For explanation:
PC downloads are still seperately listed for Hikki, although RIAJ doesn't count PC seperately anymore since January 2014.
Looks like Universal, her record company, didn't want to update her chart to merge the sales for PC and mobiel phones together. So PC is still extra for her.
Sakura Nagashi e.g. was ONLY released for PC, not for mobile phones (means not for download portals like recochoku).

Every song, which would be released for PC digital download only today, would be listed under "Single Track/Full song" as both PC and mobile downloads are counted together for full songs since 2014. But back in 2012, it still was counted seperately.