There had been several updates to the site since the last time I checked, and an actual about section. Basically, Harvest Festa takes place in one of the possible futures of the world that Kotarou rewrote at the end of Rewrite (his “rewriting” allow for infinite possibilities and such), and so the main events of the original VN never happened and everything is peaceful and all. Because the original events did not exist, the heroines all get new stories. Even Kagari transfers to Kotarou’s school, which makes the whole thing sound like a happier AU like Muv-Luv Altered Fable. More happy slice-of-life, like the common route. The site describes it as a “future like a festival.”
I’m OK with a fandisk like this. I liked the characters in Rewrite a lot, so a fandisk with more fluff is want. Rewrite HF! is due for July 27, 2012.