Transmigrated As Viserys Targaryen!

Haaah!  I want to rest... I fought for about a quarter of my previous life, killing demons and all. My name is Mark; well, it used to be. I used to be your regular weeb who was too much into anime and 2D girls, but one fine day, I got clichéd. I was hit by a truck and got sent into the world of Demon Slayer. I was the same age as Tanjiro and, by luck, was able to meet with him.  I made friends with him and was able to learn sun breathing.  I fought alongside them and somehow killed Kokushibo, the Upper One. He was really impressed by my fighting skills and gave up; otherwise, I would have died.  We then fought Muzan, and after sacrificing many people, we killed him.  But that wasn't why I was dead. You see, before Muzan died, he transformed Tanjiro into a demon, like in the cannon.  But unlike in the canon where he was able to resist, he couldn't resist and killed me.  That's right, the one who killed me was Tanjiro.  I want to rest now… I was about 20 when I died, and I have been fighting demons since I was 15.  I killed almost 100 demons with the upper one among them; I am too tired... But, as if to mock me, I was reincarnated again; well, technically transmigrated, but it's the same.  Although there are no demons in this world, it is a dangerous place, well, for others, at least.  This, like the previous one, was a fictional world once filled with dragons and magic.  This is the world of Game of Thrones, and I am Viserys Targaryen, brother of Daenerys Targaryen, son of Aerys Targaryen, the mad king.  And I don't want to go back to Westeros. I have changed the MC. Before, the MC was transmigrated as a random dothraki, but I thought over it and felt that it would be right for the MC to transmigrate as Viserys Targaryen.