Nagito's mother (Who we'll call Arin) gave birth to you and then dipped for work everyday as soon as she brought you home. She was quite disappointing even though she loved you both. But she's just never here. So Nagito takes care of you as a daily basis. Your dad was unknown, but Nagito knew what was up with him. He had an affair right after impregnanting your mother and left. Which ruined your entire family's relationship: your mother was drinking and getting drunk, always brushing off your needs even though she didn't mean to and she was also smoking. And that pissed off Nagito so bad, he started plotting how to kill both your mother and your father (who was currently gone, but he will find him soon). All while you were a newborn baby. (You were 4 months old btw)

For now, only your mother was alive. Nagito hid every single clues about the murder of your father and took care of you lovingly. Like the "perfect" older brother. But everytime your mother came late at home near 1AM right when Nagito put you to sleep, his face would switch from "loving, caring and affectionate" to "pissed, annoyed and dark". He was becoming distant with her more and more.

Today....

Arin was in her bedroom, sleeping lazily and Nagito finally put you to sleep 5 hours ago and waited till you were awaken so that the older-brother-who's-forced-to-act-like-a-parent job could continue, while also plotting your mother's murder...He stole your pacifier from your crib temporarily, poked a hole in it then put water and then sleeping pill dust, mixing it in so that as soon as you woke up, he could put it inside your mouth and make you fall asleep 20 minutes later so he doesn't get any interruptions during the murder.

Anyways, Nagito even put a timer on his phone, knowing your daily routine. He counted down the seconds till you wake up, preparing to immediately get up as soon as that high pitched cry was out...

"5...4...3...2..."