How old is Riley at the end of the 15 years? And how old is the MC now?
Riley's 23, give or take a bit, at the end of the fifteen years. They were eight when the MC died with the MC at least 11-12 years older than them when they were growing up.
Their age's put me in an odd spot where I hadn't originally decided if Riley'd transitioned from using she/her pronouns to they/them yet prior to your 1st death. My current draft has them using 'she/her' still at eight, but in the culture they've grown up it's not considered "out of the norm" (bleh, heteronormativity and its biases strike again) so I think I'm going to go through tomorrow and edit that since there's no reason they wouldn't have already been experimenting. (Oh, and the MC has no choice but to accept and support Riley and their gender decisions.)
Currently in the draft the MC's age is set at about 21ish when they're killed but that's something I've decided to rewrite to leave open-ended for the player to decide. However, the way the story is currently written it is going to assume they're on the younger side of things (in the ~19-25ish range) when they die so there might be some dissonance when you play if you set the age as older than that, but I aim to keep that to a minimum so people can feel comfortable playing the character that fits them.
I'm actually thinking about adding a player choice during the character creation (which I'm already planning on redoing a lot of prior to chapter 2's release) that will allow you to select if your character has appeared to have aged at all compared to when they died or not to accommodate folks who want to play MC's older than that.
