"Sobaniirune," the second single by female vocalist Thelma Aoyama, has become the first song to sell 2 million full-track downloads in Japan, according to her label, Universal Music Japan (UMJ).

As is the norm with Japan's digital-music market, mobile downloads accounted for just over 90% of digital sales of "Sobaniirune."

The track, an ode to the singer's long-lost boyfriend featuring Japanese rapper SoulJa, was released by Universal Music Japan in two stages. "Sobaniirune" debuted digitally as a master ringtone on Dec. 7, but sales took off when it was released as a full-track over-the-air download and a physical CD single on Jan. 23.

UMJ says "Sobaniirune" ("I'll Be With You") has so far sold 7 million digital formats, including 3.4 million master ringtones, 2 million full-track downloads and 1.6 million ringback tones, putting it at No. 1 for three straight months on the Recording Industry Assn. of Japan's monthly digital download charts. The label says the track is also 2008's top-selling physical CD single so far in Japan, selling more than 550,000 copies to date.

"We think that this is a historic achievement resulting from the perfect encounter between a great work by a talented artist and new technology," says Ryo Miyamae, general manager of UMJ’s digital division. "I would also like to emphasize here is that not only digital but also physical (product) has sold very well. We believe that this is an ideal success model that record companies should pursue."

Helping power sales of "Sobaniirune" was the track's use in a TV commercial by NTT DoCoMo, Japan's biggest mobile carrier.

The single is a response to the 2007 hit by SoulJa, "Kokoniiruyo ("I'm Here for You)," which also featured Aoyama. "Judging by the success of 'Sobaniirune,' the 'answer song' remains as fresh and appealing as ever to today's music fans," comments UMJ president/COO Kazu Koike in a statement.

"In addition, we're gratified that our marketing and promotional synergies between physical and digital worked so well for Thelma, as they have previously done for our artists GreeeeN and SoulJa," adds Koike.