It is as it said, you might or might not have heard of KaiCenat but he's a big twitch streamer who ushered in an era of negro on twitch. All those yellow dots are streamers of the black skin and their viewers tend to watch eachother.
Note that while JP and Turkey is technically close to them on the map, it could be that they are all close to the FPS scene rather than that they share a lot of audience. But if you go in the site that I linked, you can zoom in/select and see which Japanese streamers have audience who watched Yamanbas.
