I created the original planning document in August 2012, one year and half before starting to write the first chapter - and even then, I created the document in order to keep in order the ideas I already had - so perhaps late 2011 or early 2012, which means I've been planning this story for two full years before starting to write it.

The backstory up until a certain point

SPOILER

Faith's death

/SPOILER

is a badfic that does indeed exist and Sergio is indeed from it - that one started in 2006 and was abandoned in 2010 so we can say that, in a way, the true spark point for Blank Sprite was actually set ten years ago.

The happenings in between are actually partially based on scrapped story and/or character ideas originally unrelated to my PPC spinoff. They helped me fill the time gap between the point where Mai Dire Fine ended (2007 in-universe) and when I had already claimed Sergio to be recruited (2009)

Every single "Turbo" I mentioned actually existed, however, some were never published (I didn't even HAVE a computer, much less an Internet connection, when I originally wrote First Turbo) and there are others that never got more than a few lines and so were never counted as an actual Turbo. The actual count might be 8-9, maybe even ten of them.

Actually, Agent!Sergio was indeed supposed to be the sixth, and a different person from the third - them being one and the same was a retcon I made around my third mission as I thought it would've been more interesting. Coming up with a way to justify him ending up in the PPC was what gave me the idea for Blank Sprite, but I only came up with the proper plot after watching Puella Magi Madoka Magica.

And, by the way, I'm actually planning to spork one of the other Turbos. I found Fourth Turbo's story still around on the net (no links - it's in Italian, so I doubt anyone here is actually able to read it), and I think it's missionable so I'm doing that as part of my future spinoff.