One, "End"'s actual name is "Kan", the scanlator just apparently believes that the name is sufficiently plot-relevant that they cannot justify not translating the name... which, IMO, a stupid and bad reason. As far as we know, it's a character of in-universe Japanese nationality with a Japanese name; it should be rendered as such.
Two, someone claimed on Dynasty Scans that they've read further into the later chapters' raws, and says that all the doomsayers believing "End" is a danger to Miwa and Saeko's relationship are wrong.