She is 8. Though she has the memories and the knowledge of a middle aged Japanese woman that just so happened to be a complete psychopath. Which makes her a very dangerous (and messed up) 8 year old.
Reading this manga I always thought the relationship of these two is kinda toxic and things could get real ugly if it took a wrong turn. Then I read the LN and oh boy,
Description is kind of wrong, because this manga is actually both official and non-canon at the same time (every SCoOW manga is an official touhou project manga, but only the manga written by ZUN are canon).
It is incredible that everyone of the main cast here are such wrecks that the typical annoying bitchy secondary character that intrudes on these stories to introduce drama feels like a nice person in contrast.
Yeah, Satou is very, very far away from a self-insert protagonist. If Chinatsu wasn't super pretty it would be a classic shoujo story, actually, considering how much Satou is a catch (there is a hilarious scene related to that that I can't wait to see in manga form).
it is not the author calling her a slut, that's kyotaro ("my sister" is a dead giveaway that the line is in his voice). and we all know how judgemental kyotaro is with strangers/acquaintances
don't worry. the series will get into a little slump after this climax, but it quickly picks back up later on. be aware that the manga is currently adapting the 4th volume out of the 11 volumes (as of today) of the LN. this story is huge and I really doubt the manga (or the anime) will ever...