so what you want to do is, after the confession scene, there is a secret option to give sayori a comically large toblerone, to do this, you need to backflip 3 times, delete monika, yuri and natsuki from the files, backflip 3 times again, save your game, then restart your game, go back onto the save, then there should be an option to give her the tolberone.
once you give her the tolberone, you should see this screen[media.discordapp.net] for about 10 years (depending on what specs your pc has, if your pc is a literal trash can then you're gonna be waiting a few decamillenniums)

after that, you will reach the end of the game, except sayori sings your reality not monika. (honestly fire)

that is all.
thanks for reading

:3