Osomatsu-san x Reader One shots Book 2

Baby sister (Matsuno brothers x Baby sister!Reader)

Requested by s728892

I apologize that it took so long and I hope you like it

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Everything happened so fast. Ten months ago, Matsuzou and Matsuyo told their sons that their mother is pregnant, so they will get a little sibling. Of course, the brothers freaked out and didn't knew how to deal with this at first. After all, their sibling would be a baby while they are adults. Still, the more time passed by and they found out they get a baby sister, the sextuplets got a little excited. Matsuzou told them they need to help of course, but at the same time they can teach their baby sister what she needs in life.

Maybe.

One month ago, Matsuyo gave birth to you cute little cupcake and the brothers fell straight in love with you after seeing you. Of course they were afraid to hold you in their arms, but after you all were at home, they carefully took you. Since this day, the brothers doesn't leave you one second alone. Only when you take naps in your crib.

Today, the parents left for the whole day their sons with their baby daughter alone. The sextuplets were very happy to have you all for themselves for a whole day. Normally, you are more near Matsuyo since you still get mother milk and you are a very hungry baby.

It's 6 AM and you lay on the ground on your back, staring up to Jyushimatsu who is getting your attention with funny faces. Still, you don't laugh yet and can only stare at your brother with big eyes. "And if anything happens, call me or an ambulance, understand?" Matsuyo says serious. "We know Kaa-san." Choromatsu says with a small sigh. "We will be back around 8 PM, so make sure to bring Y/n early to bed." Matsuzou looks at Osomatsu. "This was one time when I forget to put Y/n early into bed." Osomatsu sulks and crossed his arms over his chest.

After giving a small check-up on you for the last time today, Matsuzou and Matsuyo left the house.

"Finally! Y/n's Onii-chan will play with her right away~!" Osomatsu coos happy, quickly walking to the living room. The others quickly follow him, wanting to spend time with you too. This is the first time they are alone with their baby sister and you can see they are very excited.

Jyushimatsu hums confused, seeing no reaction to his funny faces. 'Maybe she is sick? Normally, Y/n is laughing when I do this.' The others entering the room and Osomatsu is the first who sit down to your free side. "Y/n~! You're Onii-chan is here~!" He coos and tickles your side very gentle. You squirm around, but don't giggle like usual. Osomatsu hums confused and stops, since you seemed a little uncomfortable. "Is Y/n sick?" "I don't know." Todomatsu says a bit worried.

"She's hungry. Just like usual." Ichimatsu sighs and walks into the kitchen, doing what his mother explained to him. Since you still drink mother milk, Matsuyo made sure to pump out some milk and filling it into your baby flasks. Since you drink much, you have for the whole day 10 flasks in the fridge. If they need some milk, they will just warm it up.

Taking a few minutes in the kitchen, Ichimatsu returns with the warm milk bottle. He is the only one who knows how to feed you, since Matsuyo explained it to him. "Let me feed her, Ichimacchan~!" Osomatsu tries to take the bottle out of Ichimatsu's hand, but gets stopped from Karamatsu and Choromatsu. Neither of them know how to feed you right. Matsuyo explained to them that you could choke on the milk if they hold the bottle wrong. Even if Ichimatsu said he can never take so much responsibility, he is the only one who would be calm enough to feed you without freaking out. He is doing this from the inside.

Ichimatsu picks you carefully up and makes sure you are in the right position. The others watching closely how to do this. Once you are comfortable, Ichimatsu press the warm milk gentle against your lips. You hesitate at first, but open your mouth and suck slowly on it. Once you notice that milk comes out of it, you start to suck more on it and drink faster. Your brothers blushing softly, seeing you for the first time eating. Normally they don't watch you eating, since they don't wanna see their mother's breasts. Todomatsu quickly makes takes out his smartphone and makes a video.