Sakura peeks out from behind the tree, relaxing slightly when her head doesn't get exploded right away. She's heard the stories from the other girls in their class, that Katsuki got mad and tried to blow them up for no reason.
She hadn't quite believed it- and not just because it was Ami and the other bullies who had been complaining about it loudly enough for the whole class to hear. From what Sakura has observed so far about Katsuki since the beginning of the school year - only a few weeks, granted - he's not the type to actually hurt anybody. Sure, he glares and scowls and curses, but he's never attacked anybody, and he's never exploded anybody.
She suspects part of it is because he's an Uchiha. His clan - and possibly close family, like his parents - are the main police force in the village, after all, so it makes sense he wouldn't want to get in real trouble when it could be his dad or his brother sent to reprimand him. She wants to disappear into the floor whenever her mama or papa get onto her at home, and she can only imagine it would be way worse if they were police too.
Another reason she hadn't believed the rumors is because she's seen with her own eyes that Katsuki will argue with just about anybody - up to and including Iruka-sensei - but he only ever gets really mad when someone says something mean about Naruto.
Sakura's heard stories about Naruto, too, well before she ever stepped foot in the Academy. Things adults would mutter angrily to each other when he would run past or warnings to their children as they tugged them away at the playground. Things like demon or devil child or no good. Her own parents have never warned her against him, but they've never stopped the other adults from saying mean things, either.
Sakura knows what it feels like to have people say mean things about her, to her, and…it doesn't feel good. It hurts, and it makes her cry, makes her run to her mama and papa to be picked up and comforted, and only then does she feel better again.
Naruto doesn't have parents. He doesn't have anybody to run to when people say mean things and make him cry. Nobody but Katsuki, who Sakura figured out very quickly is like a pricklier, angrier, boy version of Ino.
Ino would never really hurt anybody either, and that last comparison is what finally made her set aside her shyness and set off alone to find the boy like Ino and the boy who - for all his fox smiles and bright laughter - is, probably, just like Sakura.