This is mostly a chapter written for my own amusement so don't take it seriously.

Izuku Midoriya:

He began muttering facts about the enemy as the enemy stood before you two, ready to murder you both, so you gave the back of his head a slap, snapping him out of it. He mumbled a quick sorry as he began focusing on the battle.

Katsuki Bakugo:

A kid bumped against him so he was ready to scream at the top of his lungs so you slapped the back of his head, asking if he wants to traumatize the damn kid. He huffed and told the child in a grumpy, not shouting voice to look where they run.

Shoto Todoroki:

You asked him how you look in your new clothes, and he began telling you about how bad your outfit is and began naming up the things bad about it so you gave the back of his head a soft slap to shut him up, telling him you understand and he doesn't have to start naming it all. He just rubbed the back of his head, mumbling he thought you wanted an honest opinion.

Ochaco Uraraka:

She was rambling about something, floating without even realizing. Her head was to you so you gave the back of her head a soft slap but hard enough to snap her out her rambling so you can tell her she's against the ceiling, to which she gasped and then yelped when she released her quirk and crashed on the floor. When you held your hand out, she let otu an embarrassed laugh, thanking you as she took your hand and got up.

Tenya Iida:

He was yelling instructions and your head was hurting so you just slapped the back of his head, angrily telling him to be quiet because your head feels like splitting. He just stared in shock at you, his glasses having fallen off. He picked them up, telling you there was no need for that and you could have had just told him and he would have been more quiet.

Eijiro Kirishima:

He noticed your hand moved to his head so he made his skin hard without a second thought, only to curse when you cursed and shook your hand in pain. He apologized, taking your hand and rubbing it before he frowned, asking why you were even gonna slap him. When you said you wanted to see if he would see a surprise attack coming, he couldn't help but laugh before he said he saw it coming.

Tsuyu Asui:

She noticed a fly so you told her not to eat it. She chuckled, finding it amusing you said that but then stuck her tongue to it so you slapped the back of her head. She stared in shock in front of her, her tongue sticking out her tongue, confused. When you apologized, saying it was a reflex so you couldn't control it, she laughed and shook her head, saying it's okay and it was actually a bit funny.

Momo Yaoyorozu:

You were both in a battle and she was trying to come up with a plan but she was panicking too much for it to work, so she turned to you and told you to slap her. When you asked why, she told you in an unsure tone that it might help her stop panicking and focus. When you slapped the back of her head, she let out a gasp, not having expected the sudden, harsh slap. When you apologized, she shook her head quickly, saying it's okay before she gasped, saying it worked and quickly began coming up with a plan.

Denki Kaminari:

He was in his dumb state so you got curious if you give the back of his head a good slap if it will knock some sense in, so you did. It just resulted in him stumbling, hitting his own foot and then falling face-first on the ground.

Kyoka Jiro:

She was listening for the enemy when she suddenly screamed so your hand moved on it own to slap the back of her head, which worked to make her stumble and her earjack pull out the wall. She looked at you with shock so you were quick to apologize, saying it was a reflex. She rubbed the back of her head, mumbling it's fine.

Fumikage Tokoyami:

You were joking around with Dark Shadow when it reached out to grope you to tease you so you slapped his cheek, forgetting your hand would just go through and slap Fumikage who stood behind Dark Shadow. Fumikage was very confused when suddenly a harsh slap was on the back of his head. He held it, making a confused noise, watching as you apologized, promising him you didn't mean to hit him and it was for Dark Shadow. When you both heard Dark Shadow laughing, both stared, realizing it meant for this to happen. Fumikage sighed, saying he should be the one apologizing for not having taught Dark Shadow manners.

Mina Ashido:

There was an insect on the back of her head so you moved without thinking. When Mina suddenly felt the back of her head get slapped, a gasp came out her before she turned and stared at you, only to begin laughing when she saw how confused you looked at what you just did. When you said there was an insect on her head and it was the first thing in your head to do, she chuckled and wiped the back of her head, saying it's fine, even praising you for how good that slap was.

Yuga Aoyama:

He was flirting and doing weird poses so you gave the back of his head a soft slap as you walked past, telling him to focus. He gasped, saying you ruined his hair. When you told him it's fine, he pout and told you not to do that again.

Eri:

You slap this traumatized child and this child will never look at you the same way and tremble whenever you come near in fear that you will do it again and wonder what she did wrong and if she made you upset/disappointed. In other words; don't slap this child, even if it's a soft slap.