Ughh I live this type of trope ngl,,, but try "Hooky" in webtoon! It's about twins and started off bright and light-hearted, but things turned south somewhat in the middle when something happened to one of the twins.
Next, it'd have been this one https://www.mangago.zone/read-manga/black_haze/ the artist remade the series but it will take a darker turn in the future.
https://www.mangago.zone/read-manga/houseki_no_kuni/ Light and happy turns very dark
And anime/manga called "Made in Abyss" where things take a dark turn
ahhh thank you my loveeee
You're welcome!!
anything like “i’m not that kind of talent”
- starts off funny but slowly takes a dark turn
- the mc went through horrible shit and genuinely wants his revenge