Hikari Yagami (夜神光, Yagami Hikari, reading unverified) is the child of Light Yagami introduced in Death Note: Light Up the NEW World. Conceived in secrecy, the child was intended to take over the mantle of Kira after Light's death.
Very little is known about Hikari and very few people even knew of his existence. It is known from Ryuk that the boy was easily corrupted by the power of the Death Note and became mentally unstable. This caused Hikari to become a merciless killer despite his young age. It is also known that he was not on good terms with his foster father, Teru Mikami, and was eventually betrayed and killed by Mikami.
The novelization of the film goes further into detail about Hikari's personality, revealing him to be an abusive, threatening individual who went as far as to treat Mikami as a slave.
In Death Note: New Generation, Hikari is not directly seen, but he has a presence in the first episode Mishima's Chapter: Rebirth. After Rokuro Natsugawa has been taken in for questioning by the task force, Hikari writes his name in the Death Note, controlling him to repeat over and over that he is Kira and the Death Note has been resurrected. Natsugawa then attempts to commit suicide by biting his tongue, but the officers with him stop him and he dies of a heart attack. After that, criminals begin dying like they had years before, killed by Hikari.
In the film Death Note: Light Up the NEW World, Hikari is first referenced when Tsukuru Mishima is being questioned by the Task Force. They accuse him of hiding evidence on his computer, including the information that Light Yagami had fathered a child. Mishima denies all of this, since at the time he does not have his memories of these events.
At the film's climax, Yuki Shien reveals that Light fathered a son before his death in case anything were to happen to him. Named Hikari, he was first raised in the United States before Mikami was appointed the child's guardian. Some time after Light's death, Hikari was brought back to Japan by Mikami. In 2015, Ryuk gave Hikari a Death Note. After becoming insane from using the notebook, Hikari is killed by Mikami, who takes the notebook for himself. Tsukuru Mishima, who witnessed Mikami killing Hikari, shoots Mikami to death.
- Hikari's name is only seen written in the Death Note by Mikami, with the characters "神光" seen on the page.
- Hikari's name is never spoken in the film, so the exact pronunciation is unknown. Hikari's name, written 光, means "light" in Japanese and is usually read as hikari. Other possibly pronunciations include Kaizechuu, Koukun, Koushou, Kouji, Kousou, Teru, Hiroshi, Mitsushi, Mitsuji, Mitsutsugu, and Mitsumune.
- Hikari is also not named in the novelization; he is referred to as "Light's son" and "the boy."
- Ryuzaki states in December 2016 that Hikari would be nine, placing Hikari's date of birth in late December 2006 or sometime in 2007.
- http://mikami.tumblr.com/post/166930043856/hi-i-read-your-post-on-ltnwmikami-and-you blog post by Luna. 2017 30 October.