One possible manga could be 'Monster Musume no Iru Nichijou'. It has characters that may seem scary at first but have a sweet side.
It might be a fantasy manga where the kind and sweet girl has magical powers and uses them to help others. Or it could be a slice-of-life manga that showcases her daily life and the kindness she spreads around.
It could be a horror manga where the girl has supernatural powers or is involved in creepy situations.
One such manga could be 'The Enigma of Fearful Expressions' where the main girl constantly has terrifying expressions for various reasons.
You might want to check out 'Spooky Smiles'. In this manga, a girl has a smile that sends chills down your spine. The art style really emphasizes the scariness.
It might be an adventure cartoon where a sweet girl needs to find a special apple to save her village. Another possibility is a fantasy cartoon where the apple grants the girl some special powers.
It could be a horror manga where the girl has a creepy appearance or behaves strangely to give that scary impression.
It could be a horror manga where the girl's scary face plays a key role in creating tension and scares. Maybe she has some supernatural powers related to it.
One such manga could be 'XXX'. In it, the main character is presented as a boy initially but is later revealed to be a girl. The plot twist adds a unique layer to the story.
You might want to check out 'The Mysterious Butler.' Here, the butler appears to be male at first but is later discovered to be a girl. It's full of surprises and keeps you engaged.
I think it could be a manga about a magical bakery where the treats give off a sweet caramel scent.