This is a webtoon fanfic type deal.
Basically documenting how dude was being an idiot clowning Japanese people for dying in Nagasaki and Hiroshima, while throwing in some fantasy elements, like with the Hashira from Demon Slayer
There is no racial stereotyping of the Black dude in this video, no. What dude is saying towards Japanese people can be seen as such, however. He's doing the equivalent of a Japanese person going to South Africa, putting a camera in front of Black folk, and laughing about Apartheid.
Japanese people are particularly sensitive about the bombings of those cities. They look at what we did to them as an atrocity (and it kinda was), so making fun of the atomic bombs is sacrilege to them. I had a conversation with my (Japanese) girl at the time about this. I was saying how it was basically necessary as the Japanese would never surrender, and she looked at me like I killed her mother. It was a crazy experience because I was just talking about history, and she felt like I was denigrating and celebrating what happened.
The younger generation (post 1945-1960s) literally don't know the part Japan played in WW2, because their government covers it up and sanitizes it in the history books. They make themselves look like innocent victims when we bombed them, and there are memorial sites in both Nagasaki and Hiroshima that attract a lot of Japanese visitors. Heck, they have memorials for documented war criminals from WW2. This is why a lot of them are confused about why Koreans and Chinese people hate them so much. They are the functional equivalent to White people tossing their hands up when we bring up Jim Crow and slavery.
en.wikipedia.org