I feel so bad! Ending 12 isn't too hard to get but you might be disappointed LOL. It's another bad ending (but it does have voice lines! So glad you like the game ❤️❤️❤️)
spoiler⬇️
Don't ignore Yasha, but do play normally/mixed playthrough/don't be too nice/suspicious - taking one of the routes that takes you to the final Yasha confrontation.
When see Sage at the convenience store, choose Not to comfort Sage. Don't talk to him privately/in your room (or just don't agree to the plan) and don't text Sage.
Then when Yasha comes to your house, don't strangle him or stay calm -- just run to the subway.
If you try to Push Yasha from there, because you didn't strangle him to weaken him... ;-; you get Ending 12 haha.
Here is the CG sketch for it BTW! It is not in the build yet, so you're the first to see! 💖
Thank you so much for playing again!!!
