Higurashi no Naku Koro ni, Yakusoku no Neverland Recommendations
Both of these shows have a combination of sweet and innocent moments but before you know it turns on its head and turns disturbing fast.
You will be standing on your feet for much of the scenes wondering what is going on and what will eventually happen. They like to delay the darker moments and you can differently feel the fear the characters of both series are experiencing under different circumstances.
Both shows follow a group of children trying to solve a mystery. The characters have a similar feel around them, and the shows are of the same genres (Horror & Mystery).