Superflat as defined by japanese (philosopher) Hiroki Azuma:
On one side, there’s the database generated by anonymous who reassemble or dismantle existing elements – it’s the “super” part.
On the other side, it’s simulacra embodied by cultural products, fantasm, audience’s desires, consumption – it’s the “flat” part. At some extent, you can see some similarities with memes (ie, aren’t we all creative anonymous?).
It takes also into consideration the Japanization of US culture during the postwar period, which created an identity crisis in Japan – on this point, Azuma says “now Japanese society has been so deeply Europeanized and Americanized that any nostalgic return towards its traditional, original, or “pure” Japaneseness, seems a fake“.
Takeshi Koike’s Redline seems to fit exactly Azuma’s definition of Superflat; the Western visual influence, the attractive simulacra with literally “flat” characters or the perfect romance, the database with tons of tributes & unrelated or “non-narrative” elements.
It’s animation for animation’s sake, a colorful ride where the fun comes from the Redline race itself. It’s about consuming an experience, as crazy as it can be. And while talking about otakus, Azuma shared this idea, “they don’t need narratives, they don’t need objectives. They need communication [...] Maybe otaku entertainment is now only a kind of platform” (source, pdf).
On the other hand, Hiroyuki Imaishi’s Panty & Stocking, or even the live-action Speed Racer film, can be looked at as some more challenging/self-aware Superflat productions.
With the idea of reaffirming the american origins of the Japanese (otaku) culture, using the database to reveal its absurdity/emptiness/vulgarity – starting with the heroines’ names, or on the contrary, transcending the database by giving back to the cultural products/archetypes their original value – the Hero’s journey.