Shinigami Eyes

Shinigami Eyes (死神の目, shinigami no me), also known as Shinigami Eyeballs or Eyes of the Shinigami, are eyes which can see both the names and lifespans of humans floating above their heads.

Eye deal
Making the Shinigami Eye Deal is the most common way for a human to obtain the Shinigami Eyes. A human Death Note owner can make the trade with the Shinigami who possess them, and gain the eyes in exchange for half of their remaining lifespan. A human can never regain the fraction of their lifespan that has been sacrificed in exchange for the Shinigami Eyes, even if the human loses ownership of their Death Note and their Shinigami Eyes. Each subsequent deal will again half their remaining lifespan.

The eye deal is first mentioned by Ryuk when he offers Light Yagami the trade so that he can get the name of the man following him. Light refuses, as he is unwilling to give up half his lifespan.

The first person shown to obtain the Shinigami Eyes this way is Misa Amane, who makes the deal with Rem.

From birth
In the novel Death Note: Another Note, Beyond Birthday is said to have been born with Shinigami Eyes. It is never explained how a human could be born with the eyes, though the idea of a Shinigami losing his or her eyeball and then dropping it to Earth was jokingly mentioned in the story.

Appearance
A person's eyes look no different after they gain the Shinigami Eyes. It is impossible for humans to tell (scientifically or otherwise) who possesses Shinigami Eyes.

In the manga and other adaptations, the eyes are sometimes depicted artistically for the reader/viewer's benefit. In the manga, a human's Shinigami Eyes are depicted as having gold pupils, with red irises and pale yellow sclera. In the anime, the irises are simply a bright and shining red.

In the film series, the eyes are depicted differently between the films. In Death Note: The Last Name, they are depicted with a yellow "cat eye" appearance. In Death Note: Light Up the NEW World the eyes have a dark red color.

Abilities
Humans with Shinigami Eyes have the ability to see the names and lifespans of other humans, making it easier to write their victims' names in their Death Notes. However, just as Shinigami cannot see each other's lifespans, humans cannot see their own lifespans or lifespans of other Death Note users.

Regardless of their original eyesight, those with the eyes gain a visual acuity of over 3.6 (about 72/20).

Restrictions
The Shinigami Eyes can only make a person's name and lifespan visible under certain circumstances. A side view of a person's face is enough to be able to see their name and lifespan. A person's eyes must be visible in order for it to work, but if they are wearing sunglasses while their entire face is visible, it will work. It will also work If half a person's face is seen vertically.

Circumstances where the Shinigami Eyes will not work to see a person's name and lifespan include seeing the back of a person's head, seeing the lower half of their face (i.e. eyes are not visible), and seeing their body but not their face.

A photograph of a person is also acceptable, and follows the same rules as listed above. The only exception to this is when the person in the picture is deceased, in which case their name and lifespan will not be visible. While photographs work to see a person's name and lifespan, drawings do not work, no matter how lifelike or accurate they are.

If an individual with Shinigami Eyes looks into a mirror, they will see their name, but not their lifespan. As Rem explains, this is because it is unnecessary for one to see their own lifespan.

Misa Amane
Misa Amane is the first character to be depicted with the Shinigami Eyes in all incarnations of the franchise. She makes the eye deal with Rem in order to find Kira, which she does successfully. After introducing herself to Light, she tells him that she will be his eyes and she'll kill L for him. She meets L, but she doesn't know it's him and is immediately apprehended on suspicion of being the Second Kira. Misa gives up ownership and loses her memories of the Death Note and the Shinigami Eyes. After regaining her memories and uncovering the buried Death Note that Light left in the woods, she makes a second eye deal, this time with Ryuk, essentially quartering her remaining lifespan.

After the timeskip, Misa continues to use the power of the eyes up until Light orders her to forfeit her Death Note and pass it on to Teru Mikami, causing her to lose her memories and the Shinigami Eyes once more. After Rem's death, her remaining lifespan was transferred to Misa, though the question of how many years Misa had left remaining is unknown, as Death Note 13: How to Read reveals that Misa committed suicide a year after Light's death (this is also implied in the anime).

In the film Death Note: The Last Name, Misa makes the eye deal and loses her memories and the eyes while in confinement, as she does in the original. She makes the eye trade again with Ryuk, but only loses her memories of the Death Note and the eyes after Light's death when L burns the notebooks. Ten years later, in the film Death Note: Light Up the NEW World, Misa makes the eye trade a third time, again with Ryuk. She looks at a picture of Light and confirms that he is dead, which she shares with Yuki Shien. She sends Shien on to complete Light's work, and she kills the Task Force members Uei Uragami and Shin Kuromoto to help him escape. She then writes her own name on Death Note paper, dying peacefully "in the arms of Light Yagami."

In the 2015 television drama, Misa does not make the eye deal a second time. Instead, Teru Mikami has the Death Note stolen from her immediately after she digs it up, and he makes the eye deal. Misa continues working with Light to help him as Kira after losing her memories and eyes. The TV drama also indicates that having the Shinigami Eyes causes eye strain, and Misa uses eye drops in the days after making the eye deal.

Kyosuke Higuchi
Kyosuke Higuchi makes the eye deal with Rem. In the manga and anime, Higuchi (as the Third Kira) is at first reluctant to obtain the Shinigami Eyes since, like Light Yagami, he intends to enjoy a full life and the fruits of his work as Kira. He even plots to seduce and marry Misa Amane since her possession of the Eyes could be useful in his plans. Circumstances, however, force him into making the deal with Rem when someone, whose name he cannot otherwise obtain, threatens to name him on national television. Higuchi actually uses the eyes in order to kill a traffic cop who has pulled him over for speeding. In the end though, his time with the eyes is short-lived as he winds up captured and dies shortly after, Light having written his name down on a piece of the Death Note.

Higuchi's use of the eyes is similarly depicted in the 2015 television drama.

Kal Snydar (a.k.a. Jack Neylon)
Jack Neylon (real name Kal Snydar) makes the eye deal with the shinigami Sidoh in the manga. After Sidoh discovers the Mafia hideout, a subordinate of Mello known as Jack Neylon (real name Kal Snydar) is made to go through with the eye deal. In the first failed raid on the hideout, Jack reads out the names of the names of the Special Ops team as Sidoh unmasks each of the members. Each person's name was then written down by Rod Ross in the Death Note. Neylon/Snydar later dies during the second raid, as Light had written his name down in the Death Note, along with other Mafia members.

In the anime, the eye deal and the first raid of Mello's hideout are left out entirely.

Soichiro Yagami
Soichiro Yagami, Light Yagami's father, makes the eye deal in both the manga and the anime as part of Light's plan to infiltrate Mello's hideout the second time. Light intended for Matsuda to make the deal, but Soichiro accepts instead.

With the power of the eyes, he is able to see Mello's true name (Mihael Keehl), but is shot by one of the few remaining Mafia members and is fatally wounded when Mello detonates charges and destroys his hideout. Light desperately tries to persuade his dying father into writing down Mello's name in the Death Note, but Soichiro will not. He is relieved to be able to see Light's lifespan before succumbing to his wounds, dying with the belief that his son isn't Kira.

In the films, Soichiro never gets the eyes and doesn't die, as there is no timeskip or the events of Part II. Unlike his manga/anime counterpart, however, he does learn that his son is Kira.

Teru Mikami
Teru Mikami makes the eye deal with Ryuk after gaining Misa's Death Note. He remains with the eyes all the way up to his death. Although the eye deal would have cured him of his vision impairment, he still wears his glasses from time to time, likely to avoid suspicion.

C-Kira
C-Kira ("Cheap Kira"), true identity unknown, is the catalyst of the post-series one-shot, where he/she kills off the elderly and sick, as well as people who wish to die. Though his/her identity is never revealed, he/she is depicted with Shinigami Eyes, presumably having made the eye trade with Midora. C-Kira commits suicide at the end of the one-shot manga when Near calls him an "abominable murderer" after announcing that he has no interest in the case.

Beyond Birthday
Beyond Birthday was born with Shinigami Eyes. He is the killer in the LABB murder cases discussed in Death Note: Another Note. Although it is never explained how a person can be born with the Shinigami Eyes, Mello jokes in the novel that a Shinigami might have dropped his or her eyeballs to earth instead of a Death Note.

Kiyomi Takada (film)
Kiyomi Takada does not make the eye deal in the manga or anime, but her story is changed in the film series. In the second film Death Note: The Last Name, the Yotsuba story arc is removed, with Sakura TV and Kiyomi Takada serving in place of the Yotsuba Group and Higuchi, respectively. Takada gains the Shinigami Eyes from Rem, but as in the case of Higuchi, winds up captured as Kira and killed by Light's piece of Death Note.

Sakura Aoi
Sakura Aoi makes the eye trade with her shinigami Bepo prior to the start of the fourth film Death Note: Light Up the NEW World. She uses her ability to walk through Shibuya, killing random pedestrians as she passes by. She is tracked by the Task Force and killed by Yuki Shien.

Tsukuru Mishima
Tsukuru Mishima made the eye deal with Ryuk prior to the events of the fourth film Death Note: Light Up the NEW World. He recalls this in flashback when he uses his abilities to get Ryuzaki's real name.

Yuki Shien
Yuki Shien makes the eye deal with Ryuk near the end of the fourth film Death Note: Light Up the NEW World. He intends to kill the new Kira who has impersonated Light Yagami, because to him only Light is Kira. He uses his ability to kill off the special police team coming after him, and convinces Ryuk to pull off their masks so Shien can write their names.

Trivia

 * Ryuk compares it to putting on contact lenses.
 * In the anime, it's suggested that Shinigami conduct the eye deal by placing their palm over a human's eyes.
 * Ryuk's own eyes glowed when he performed the deal with Soichiro.
 * Neither Mikami nor Soichiro showed signs of having trouble seeing with their glasses on, despite the fact the prescription would make what they saw blurry and distorted with their improved vision.