(Bakugo POV)
I leave Momo lying on the bathroom floor in pain and go looking for her sister.
"Come here, we need to talk."
She doesn't answer; that idiot is hiding.
You'll think i'm crazy but my cock can perfectly sense when there's a scared girl nearby who's ready to be submissive. Jirou is obviously both scared and manipulable to the point of submission at that moment.
When i walk past the laundry room door, my cock suddenly gets harder: that teen's frightened hormones are in the air.
With a predatory look i open that door and start rummaging through the piles of clothes belonging to the family and the servants: i find her there in a corner, all scared.
I make her stand up and she starts screaming that she doesn't want to.
"You were hiding that your sister was chatting with a boy behind my back!"
"They were just talking."
"That doesn't change the fact that she shouldn't have! Both you and she need to be disciplined. I'm doing this for your own good."
I know very well what goes on in Momo's little sister's head: i have certain information because Jirou has a bad habit of leaving his cell phone lying around (and "Denki" isn't much of a password).
I know that guys look at her mainly because of her prominent ass and that she is terrified that (sooner or later) some guy will ask her to have anal sex: a legitimate request (given that huge rear end she has) but she is afraid because she knows it would be very painful.
These are teenage paranoias but they come in handy.
"Turn around."
"Please..."
"Turn around, idiot!"
Sobbing, Jirou turns around.
"I told you i'd do this sooner or later if you didn't stop acting like an idiot" i grab her hair and pull her head back.
Jirou cries.
"Don't you dare cry, don't you dare make me feel guilty! I don't like you, you're not my kind of girl and I'm also very loyal to your sister! But it's my duty to discipline you. What i'm about to do is not for my own pleasure but for your own good".
Jirou cries uncontrollably but doesn't dare move: my hand caresses her huge ass from over her skirt. I don't particularly like her but i have to admit she has a remarkable ass.
While she whimpers i lift her skirt and start caressing her barely bare ass, groping her without any shame and enjoying the contact with that ridiculously huge marble ass.
"Now I'm going to take off your panties and teach you a good lesson. You are just an asshole with a good asshole".
She starts crying uncontrollably: "Please, i promise i'll be good, i'll behave!".
I pull down her panties, my hands slightly spreading her firm buttocks: i am the first to admire that tight virgin asshole. What a view!
"Please, don't fuck me in the ass!"
I am tempted but my plan was simply to threaten her: i must prevent the Yaoyorozu family from thinking badly of me.
"If I give up on teaching you this lesson, will you promise to do everything i say?"
"Yes, of course!"
I make a big scene in which i sigh and take on the tone of someone who is about to make a great sacrifice: "You'll have to watch over your sister in my absence. I want to know everything she does."
"Sure! But please let me go!".
I turn her towards me and slap her so hard that she staggers:
"Just try to tell me half a lie and i'll fuck your ass all night long. I won't enjoy it, because you're a flat-chested meat toilet, but i'll do it to teach you a lesson."
"I won't tell any lies!" she says, crying.
I love the fact that she's standing there with her vagina exposed at that moment: it makes her feel much more vulnerable and ready to submit.
I throw her on the floor like she's a dirty piece of clothing: her ass is so ridiculously big that when it hits the floor it makes a beastly noise.
"Pull yourself together, you ridiculous ass-in-human-form. Every time i look at you, it's crazy that you and my hot girlfriend are sisters."
Making a girl feel inadequate is one of the many ways to keep her submissive.
Jirou wipes her tears and starts to get dressed.
The night will come when she too will have to endure but this is not it.