Okay since the matter of age keeps coming up, I'm gonna come clean
I messaged Mai to practice my Japanese, I'm very new to Japanese so I'm not great and some of the few questions I know are "how old are you" "how are you" and "what grade are you in" so I used them for practice
The chat log is here. For those who don't care to look, Mai says they're in 7th grade, and as I said regarding Pixiv age it auto updates on your birthday.
I'm sorry for not just saying sooner.