Originally Posted by Nigoli
^ Sorry for the delay!
It seems to be in one of Mio's routes to her ending/s. It's in a bedroom for the CG I believe still. I'm not too sure of the choices sadly since it's been a while since I've unlocked those particular CGs. Let me know what happens.
Thanks! Tried a bunch of different routes for Mio's ending and finally got the achievement. Now at 950G. I think I will stop play here... too frustrating to try and find that last 2.xx%.