Played the game, it was definitely on the "more difficult than I would have preferred" end of the spectrum, and using the mouse to pull up/put down the phone was a bit janky sometimes, but otherwise I think the concept is fine, just please add a way of enjoying some of the content in peace (to use the gallery you need to unlock the phone which starts the game so you are always stuck on a timer).
Thoughts on the characters/challenges:
Mother - She's fine on her own, almost always turns on the lights before coming in and she has some sound queues to warn you otherwise (albeit quieter than the other character's sound queues). She's more deadly than the other characters and sometimes bad luck with the phone unlocking minigame + her showing up back to back can just make it basically impossible to survive, but she's fine (honestly I like her more in the later nights since more enemies means that is is very rare for her to spam check your room)
Thief - Loud sound queue and generous amount of time to pull up your phone make her completely fine. Only issue I ever had was her and mom coming up at the same time so I was worried she would just get me since I had to keep the phone down, but it never happened so not much to complain. She seems to be able to attack before the player starts the alarm/timer, might be a bug.
Ghost - She's fine, fair minigame, doesn't take too long to deal with it but can mess with the player a bit.
Sadako - Kind of tight mashing minigame, still lost a few times even when I was paying full attention to her. She's maybe okay for now but I'd ask to give the player more time to mash before dying, because with more challenges she might become too much of a nuisance. She also seems able to attack the player before starting the alarm/timer after the last night. Also the static noise stays even after you manage to send her away by turning off the screen, gets in the way of listening for the other sound queues, must be a bug.
Girlfriend - Girlfriend is too problematic in my opinion, she seems to operate on her own timer that does not seem to care about what the other girls are doing. The chatting minigame is fine since you can quickly deal with it, but the mouse labyrinth minigame is very finicky. It is terrible to be on a timer for it and then be interrupted by one of the other girls. Either change the minigame into something easier or make it so losing the mouse labyrinth minigame does not kill the player if they fail, they only don't unlock the image. This way filling all the hearts with the GF will be a chance for the player to try to unlock a new image OR a reward "rest" period where they don't need to worry about chatting with the GF to avoid losing. As of now I just unlocked all the images in the 1st night so I didn't have to deal with labyrinth in the later nights, but that does not seem intended.