Characters appearing in Umi No Yami Tsuki No Kage.
Warning! Due to the nature of certain trope names, there are potential spoilers. Read at your own discretion.
Main Characters
Ruka was confessed to by Katsuyuki recently, but she ran off out of consideration for her sister. When the walls of the tomb collapsed and she inhaled the odd scent, she gained odd powers that wax and wane with the moon.
Her specific infection works as an anti-body to Rumi's infection.
- Angsty Surviving Twin: The series ends with Rumi dead and Ruka mourning her lost twin.
- Attempted Rape: Several people attempt to rape her, usually as a form of punishment or torture, rather than wanting to have sex.
- I Just Want to Be Normal: Vehemently just wants to return to how things were before she and her sister got infected by the bacteria in the tomb. She especially wants to go back to how her relationship with Rumi used to be.
- Kill the Ones You Love: After mortally wounding Rumi in one final life-or-death fight, Ruka shoots her in the head.
- Pre-Climax Climax: Attempts this with Katsuyuki prior to the final showdown with Rumi because Ruka planned to die alongside her twin. But Katsuyuki doesn't go through with it because he knows what Ruka's planning.
Rumi has held feelings for Katsuyuki for a long time, only to see him confessing to her twinsister. She gained odd powers after inhaling a scent in an ancient tomb, and is prepared to use them to obtain Katsuyuki, before her plans expand beyond him.
Her specific infection allows her to put people under her control.
- Bed Trick: She gets Katsuyuki drunk and slightly addled with sleeping pills, resulting in him mistaking her for Ruka and sleeping with her.
- Love Makes You Evil: Her intense feelings for Katsuyuki, coupled with him already rejecting her by choosing Ruka in the beginning, drives her actions for most of the series. She goes so far into thinking that if she can't have Katsuyuki, the one thing she's wanted all along, then she'll use her powers to infect the entire world and dominate it, so she'll at least have something.
- Mercy Kill: What she considers her murder of the little girl Makoto, stating that she saved them from eventually realizing just what they had done.
- Tragic Villain: She initially seems to really enjoy her abilities and power to turn people into her mindless puppets, using it to mentally torment her twinsister and her boyfriend, who chose Ruka over Rumi by confessing. She even goes to far as to cause harm to the boyfriend's family as a middle finger for rejecting her. Further into the story, Rumi becomes more open about how the infection messed with her mind, and her pain over being rejected was twisted, to the point that she openly says that the hatred and desire to harm people is incessantly growing inside of her without her wanting it. The penultimate climax has Rumi outright make it clear that she's putting her last hope on a sense of returning normalcy onto a cure, only for that hope to be shattered where the cure doesn't work.
- Would Hurt a Child: Kills Makoto after receiving the piece of prescription she held. Rumi considers it a mercy kill, though.
Katsuyuki is one of the best male athletes on the school's track and field club. He confessed his feelings to Ruka and waited for an answer, aware that she might hold back because of her twinsister.
- Accidental Adultery: Feels ashamed about betraying Ruka, when he realizes that Rumi got him drunk and drugged and abused his altered state to sleep with him.
- Distressed Dude: Gets kidnapped almost as often as Ruka does, usually by Rumi.
- Intimate Healing: Undresses an injured Ruka and wraps up in a blanket to share body warmth with her.
Jean was contacted by Yuuichirou Touma regarding the infection that Rumi and Ruka have been subjected to and he headed to Japan. He was curious about the infection and wished to study it. His exact motives and alignment always seem unclear.
- Angsty Surviving Twin: Played with, as Jean never knew his twinbrother because of vanishing twin syndrome. When Ruka talks about wishing she and Rumi had never separated in-utero to become twins, Jean in turns laments that he would have liked to have had his twin by his side.
- Character Tic: Twirls a strand of his hair around his finger when frustrated.
- Greater-Scope Villain: The main conflict in the series is the love triangle between the twins and Katsuyuki, especially Rumi wanting to take him away from her twinsister, with a growing emphasis on the infection that caused their gaining of powers. But Jean appearing shakes things up, being unclear about whose side he's on and eventually works out a prescription for an injection that could cure or re-infect other people. And when he's on death's door, he scatters the prescription to other people to make things more difficult. Jean is basically the reason for the second half of the series.
- Hereditary Twinhood: His town of Karelia had an 80% birth-rate of twins. Jean himself is part of a set of twins, though his is a case of vanishing twin syndrome
, along with having a pair of twin sisters and twin cousins. - Icy Blue Eyes: His eyes are described as being an ice-blue color. It not only fits his very foreign appearance, but also matches his calculating personality.
- Prophet Eyes: Gains them when he overuses his powers, with the color draining from his irises and rendering temporarily blind.
- Walking Spoiler: Talking more in-depth about him is impossible without spoiling his growing role.
- You Can't Go Home Again: His hometown of Karelia was taken over by the Soviet Union and become a communistic country, leaving him with no place to return to after becoming a refugee in the United Kingdom.
The Prescription Holders
Unmarked Spoilers for all of these characters, simply because their existence proves that they have been infected by a strain of the twins' virus and have gained powers.
Makoto is the daughter of a couple running a small pension home. She's a little lonely because her parents are often busy running the pension and don't have time to play with her.
- Death of a Child: Gets killed by Rumi after she gets the prescription piece.
- Enfant Terrible: Uses her powers to harm people that have hurt her feelings. It's clear that her young age means she really isn't aware that 'killing' people is bad.
- No Full Name Given: Her full name is never mentioned, she's only referred to by her first name Makoto.
- Self-Made Orphan: Killed both of her parents when they wouldn't accept her with her new powers.
- Tele-Frag: The common way she ends up killing people, shoving them into solid objects until they are dead.
- Weaponized Teleportation: Her powers allow her to go through solid objects, just like the twins do, and she can shove other people and things into them, too.
Kaoru Mizunagi is a university student that lost his family in a fire. He has a severe grudge against the twins, though the real target of his disgust lies with Jean Johnson.
- Commonality Connection: It gets mentioned several times that he and Rumi are very similar, with their actions being driven by a broken heart and not knowing how to deal with their emotions. Especially when Rumi calls him out on harming people around Ruka and Katsuyuki as simply venting, clearly remembering that she herself killed Katsuyuki's parents for the same reason.
- Improbable Weapon User: Uses his telekinesis to move his earring around like a tiny, high-speed bullet.
- The Lost Lenore: His lover Emiko, who was sleeping at his place when the fire started.
- Telekinesis: His powers allow him to manipulate things with his mind.
- Tragic Keepsake: His ruby earring was intended to become part of a gift for Emiko, as it was her birthstone.
- Traumatic Superpower Awakening: His powers first manifested when he was at home, with his lack of control over them resulting in accidentally causing a fire that killed his family and lover.
Takuya Kirihara
Takuya is a motorbike racer and works several part-time jobs, intent on getting money to pay for his younger brother's many surgeries.
- Cool Big Bro: His younger brother sees him as one, although Takuya was cold to him until a while ago. He works hard to actually live up to his brother's ideal.
- Red Herring: Everything about him indicates that he's the owner of the third prescription piece, as well as being the one infected with the virus strain because of the leather gloves he wears while riding his motorcycle. It's actually Kyoko.
Kyoko Shiina
Kyoko was a third year and senior to Katsuyuki and the twins in the track club, as well as Katsuyuki's previous girlfriend. She graduated and now is a medical student, learning at her father's hospital.
- Heroic Sacrifice: She teleports in front of Katsuyuki, who was about to get hit by a broken telephone mast and its electrical wires, to save him from eletrocution.
- High-Voltage Death: Dies shortly after receiving an eletrical shock from getting hit by a broken power line.
Mayuka Morio
Mayuka invited Rumi and Ruka to her mansion because she knew about them from Jean and requested to have a piece of the prescription. She makes things a game by telling them to search for the prescription in her house, with the winner being the first to find it.
- Giggling Villain: She plays more of an antagonistic role than a full-on villain role, but that doesn't stop her from giggling a lot when entertained by their antics.
- It Amused Me: Her reason for getting Rumi and Ruka taken to her mansion and hiding the piece of prescription paper she has. It serves as a form of entertainment and game to her.
- Red Herring: Just like Kirihara before her, she's portrayed as the fourth person to have received the prescription and the virus strain that gives her powers similar to the twins. The true infected is her dog, Shin.
Shin
Mayuka's dog and considered her closest friend.
- The Beastmaster: His powers allow him to control other animals.
- Canine Companion: He was Mayuka's for a long time, then started following Ruka around.
- Meaningful Name: Named after the red star in the Antares Scorpion constellation, which is 'Shin' and written with the kanji for Heart.
Ian and Christian Johanson are identical twins and the cousins of Jean Johnson. They are marine biologists and assisted their cousin in many research matters.
- All Your Powers Combined: They are capable of using the powers from the other virus infected people holding prescription pieces.
- Angsty Surviving Twin: After Chris dies while saving Ian, the latter is left mourning his twin and keeping his corpse in a comfortable bed. Ian himself dies shortly after.
- Chekhov's Gunman: Both were shown on a family photo of Jean's early in the series and turn up towards the end with a much larger, adverserial role.
- Dead Person Impersonation: They initially mess with the twins psychologically by dressing up to look like Jean, but drop the charade quickly. It's also revealed that they dressed up and did Jean's interviews for him when he was still alive, too.
- Gem Tissue: They've been experimenting on encasing living beings with pearl matter by placing them inside of oysters for prolong periods of time. They intend to do this with the twins, before sending them to the bottom of the sea to their dead cousin.
- Identical Twin ID Tag: Averted, until Katsuyuki manages to leave a cut on Christian's forehead and he retains a scar. Christian actually mentions he's glad people are able to tell them apart now.
- Strong Family Resemblance: Their facial features are very similar to Jean's, which allows them to easily impersonate their deceased cousin with the minor addition of a blond wig.
- Taking the Bullet: Chris throws himself in front of Ian when Ruka shoots him.
- Tragic Keepsake: Ian holds onto the two pearls he and Christian successfuly made. He drops them after his death, with Rumi and Ruka each taking one. One of them coats an old picture of Jean's sisters, the other coats the prescription piece they held onto.
