Light adopts the name "Kira" as a cover. It's a clever trick. The name sounds like "killer," which fits his role as a death-bringer. But there's more. By using a name that sounds Japanese, he aims to mislead law enforcement. He wants them to think he's Japanese, hiding his true identity. So, "Kira" is both a disguise and a statement. It allows him to carry out his plan while staying in the shadows.