Your rapper!Munakata ask made me think of Hotel Transylvania, where Dracula (Munakata) just wants to run a professional and traditional hotel to change the world for monsters and dote on his child (Fushimi) while protecting them from humans (Yata), but at the end he's more open minded and raps.
So Vampire!Munakata lives in a fabulous old-fashioned hotel with his precious vampire child and an assortment of monstrous alphabet boys. Munakata doesn’t trust humans because they are rowdy and chaotic barbarians, plus once an angry mob killed the previous head of the vampire clan, Habari Jin. Maybe when Fushimi was little he was almost killed too, like he’s actually adopted because his asshole dad Niki caused a lot of problems in the human world attacking people and a vampire hunter finally came after him, killing him and almost killing his child as well. Fushimi just managed to escape and was taken in by Munakata, who of course became quite enchanted with him and decided that he would make the adorable gloomy vampire child his own. Fushimi is less than thrilled about being adopted but he hasn’t got anywhere else to go and it’s not like he can live among humans so he remains in the hotel with Munakata being doted on and loved by all the patrons.
But then say one day Fushimi decides to go down to the human world because like the charger broke on his PDA and he doesn’t feel like waiting for Munakata to get back from some errands. Fushimi hasn’t been to the human world in a long time and he’s wary of it but also figures he has fangs and knives so he should be okay. He’s sneaking around dark alleys towards the store when Yata runs into him – literally, almost running him over with his skateboard. Fushimi’s annoyed and mutters at Yata to look where he’s going, Yata’s like hey you jumped on front of me asshole. Fushimi notices that Yata’s knee is bleeding a little and maybe it makes him start to get a little vampire-y and he has to get up quickly and walk away in order to keep from attacking Yata in the middle of the street. Fushimi’s in a hurry because he only has a short amount of time before sunrise and he has to get to the store and back before the sun comes up or he’ll be stuck and could burn. He almost makes it but then say he gets waylaid by some random teenagers, he doesn’t realize it’s too late until his skin starts to burn. He’s trying to figure out a course of retreat when Yata shows up with an umbrella and herds him into a dark alley, Fushimi is all confused and Yata’s like you were staring at my bloody knee and drooling I’m not that stupid.
So after that Yata and Fushimi meet regularly in town, Fushimi sneaking out the house to talk to Yata because he knows Munakata doesn’t want him leaving. Except then Munakata finds out and is of course very concerned, like he doesn’t want his child being killed by an angry mob. Fushimi tries to convince him that Yata’s not a bad human but then maybe when he finally gets away to see Yata against Munakata’s orders he discovers a bunch of people at Yata’s place and thinks Yata’s betrayed him and called vampire hunters. Heartbroken, Fushimi decides to scoff in Yata’s face and maybe attacks some of Yata’s friends before fleeing, what he didn’t know is that Yata’s friend Totsuka filmed Fushimi coming and going without Yata or Fushimi realizing and Yata’s friends then all figured out Fushimi was a vampire on their own. They all just wanted to meet him because a bunch of Yata’s friends are dedicated to helping monsters and they were worried about Fushimi.
Unfortunately Fushimi attacking them was also seen by some random citizens who decide to round up a mob to attack the mysterious hotel where all those monsters are rumored to be staying at. Yata finds out and decides that even though Fushimi’s an asshole who attacked Yata’s friends Yata still wants to save him and Yata and his group go to intercept the angry mob. In the end Munakata gets to watch as Yata risks himself to save Fushimi’s life, all while Yata’s brutish barbarian friends go to great pains to save the hotel from being burned down by the angry mob. Munakata decides to give humans a chance and that he wishes only for Fushimi to be happy, no matter who he ends up with (and then he raps a song to show that he is Down With the Kids, Fushimi facepalms and is like I don’t know this person).