Wasn't quite sure what the deal was with Perfume's "Chocolate Disco". Did songwriter Yasutaka Nakata（中田ヤスタカ）merely throw together two unrelated words and then create the melody and lyrics? Or was he imagining Willy Wonka erecting a dance hall instead of a factory? Perhaps the psychedelic part of the tour in the original movie would have made more sense then.
As it turned out, Nakata was describing the supposed battle of wits involved with a girlfriend getting the perfect box of chocolates for Valentine's Day while the boy is strategizing his nonchalant but interested reaction to the present. It's a pretty big deal for that day in Japan and the reverse action during White Day on March 14th with the guys giving chocolates to the girls doubles the intrigue.
"Chocolate Disco" first came out as part of Perfume's 4th single from Valentine's Day 2007, "Fan Service [sweet]". It peaked at No. 31 (Baskin-Robbins in Japan is known as "31", so another sweets connection) on Oricon. The song was also a track on the trio's first original album "GAME" from April 2008 which hit the top spot.
It's another one of Perfume's perky technopop tunes but I still like the other big song from "GAME" better, "Polyrhythm"（ポリリズム）, the campaign song for the funkiest commercial about waste disposal that I will ever know. Still, "Chocolate Disco" has been a popular request at their concerts, and it has become one of the trademark songs for Valentine's Day in Japan.
Strangely enough, a classical-sounding version by Japanese pianist Marasy（まらしぃ）was used for a Toyota Aqua ad.
To get an idea about how crazy the time before and on February 14th is in Japan, you can watch the above video by kanadajin3.