Maybe the character had a bad experience with the girl before. As for living with his aunt, it could be that his parents aren't around or there's some other family situation.
The manga girl might be scared because of a sudden loud noise or an unexpected appearance of a scary character. Or perhaps she has a phobia that's been triggered.
Maybe it's because her expression and situation touch people's hearts and make them relate.
The expression and emotions of a scared shocked manga girl make her stand out. Her wide eyes, open mouth, and tense body language convey the intensity of her feelings.
The relationship can vary a lot. Sometimes it's like a big brother/little sister dynamic, full of protection and care. Other times, it could be a mutual growth journey where they both discover new things together.
Maybe she saw something spooky or had a bad dream.
Maybe there's a scary monster or a creepy scene that frightened her.
Maybe there's a creepy monster or a sudden loud noise that frightened her.
Maybe she saw something creepy or had a bad dream.
Maybe she saw something creepy. That could be a monster or a spooky place.
Maybe she saw something creepy or had a bad dream.