Moeka Kiryuu (桐生萌郁, Kiryū Moeka) is a tall girl that Rintarō bumps into in Akihabara. She is on a search for the IBN 5100 personal computer.
Moeka's physical features include pale toned skin, chestnut brown hair and a tall and skinny profile. Her outfit consists of a white button up top with black arm cutouts, a checkered belt, short black skirt, and black heels.
Moeka is extremely shy, her preferred form of comunication being via text messaging even if the person she is "talking" to is right in front of her. As such, she is very protective of her phone and becomes agitated if someone tries to take it from her hands.
Moeka seemed more or less interested in Rintarou, calling him Okabe-kun, and constantly sends him emails as attempts to talk to him, though this is unclear if she wants his company or simply because she has been ordered to. Her habit of constantly spamming his mailbox with lengthy SMS's made Rintarou ignore them, much to her dismay.
In one of the drama CDs, Moeka narrates a message she sent and sounds like a completely different person.
Moeka can apparently type and send SMS's at the speed of normal speech, which leads to Rintarou calling her "Shining Finger".
Moeka fell into a deep depression for an unknown reason and decided to kill herself. At that moment she received a mail from the enigmatic FB, changing her life forever. Seeing FB as the person that gave her life meaning, Moeka devoted every waking moment to carrying out her given orders, developing a dependancy on FB and the mails provided. While she is capable of carrying out atrocities for acceptance, Moeka strives to be loved and has the potential to be a good person if led in the right direction.
Her blind devotion to FB is fruitless, however, as she was considered no more than a pawn on SERN's board and is "expendable".
Rintarou first encountered Moeka around the RadioKaikan building when he was revisiting the "satellite crash site". Moeka took a few pictures of him, which irritated him; despite his orders her to stop, she persisted. Rintarou then offered to exchange e-mails under the condition that she stopped. She immediately began sending him text messages before leaving. Moeka was apparently a reporter for a magazine called Arc Rewrite, according to her introduction.
After floods of text messages, Moeka visits Rintarou's lab and demands to see the IBN 5100 (as she was the one who suggested it to him). Without asking, she attempted to carry the computer away (before crumbling under the box's weight). Rintarou reluctantly dubs her "Lab Member 005" to prevent her from leaking the IBN's secret. She also requests to send a D-mail in order to prevent herself from buying a new phone.
After the Future Gadget Lab perfected the time-leaping mechanism, a team of Rounders, led by Moeka, storms the lab and holds its members at gunpoint. She ordered them to hand over the IBN, while shooting and killing Mayuri Shiina for being "expendable", causing Rintarou to panic. She points her gun at him and prepares to shoot, but Suzuha Amane rushed in and took out the whole Rounder squad, and entered a standoff with Moeka in quick succession, giving Rintarou his chance to time-leap back in time to prevent the attack.
Rintarou tracked her down and attempted to force her to abandon her assault, but was captured by her Rounders. The group then proceeds to breach into the lab and kills Mayuri, again, prompting Rintarou to leap into the past.
Moeka continues to kill Mayuri again and again in Rintarou's various plans to save her.
A few days into the past, Rintarou visited her house to revert her D-mail and convince her to cancel the attack, only to find police officers around her apartment; she had already hung herself. He time-leaped again, and returned to her house at night. Moeka seemed catatonic, mumbling to herself while typing uncontrollably. Rintarou attempted to wrest the phone from her hand, causing her to violently revolt. He succesfully sent a D-mail to the past, but nothing changes (as the phone Moeka convinced her past self to change did not appear). After pinning her to the ground, telling Moeka both about her imminent death and FB had most likely betrayed her, she told Rintarou the story of FB and how they became a mother figure for her. Rintarou also figured out that Moeka actually D-mailed herself the location of the IBN.
Realizing that a D-mail from FB's phone could cancel Moeka's, Rintarou decided to hunt for FB by staking out the IBN drop-off point. After Moeka joined the stakeout, the two pursued the IBN and witnessed it being passed along by different people, one such person being Rintatou's landlord, Yuugo Tennouji. The two visited Yuugo while Kurisu waits outside his house. While Rintarou confronted Yuugo about his secret identity, he called Moeka "M4" a codename that FB had given her. Pulling a gun on Moeka, Yuugo admitted that he was FB, pretending to be a woman to appeal to Moeka's insecurity; he also informs the two that Rounders who locate an IBN 5100 are slated for death. Yuugo instead proceeds to kill himself to, much to Moeka and Rintarou's despair.
In retrospect, Rintarou believed that Yuugo cared about Moeka's well-being, and spared her life in a last-resort effort to protect her. Unfortunately, Moeka's death in that world-line was guaranteed, but this time around, it was Nae who killed Moeka; Nae then warned Rintarou that she will kill him in 2025. Moeka apologized to Rintarou for Mayuri's death, believing that her death is her punishment for killing Mayuri in another world-line. Reminding himself that Moeka did not kill Mayuri in this timeline, Rintarou forgives Moeka as she dies, then sends the cancellation D-mail (unless the player decides to wait it out, in which case Rintarou time-leaps so he can interrogate Nae about his death in 2025).
In the anime (a different world-line than in the visual novel), Yuugo tooks Rintarou, Moeka and Kurisu to an empty construction lot. Yuugo instead decides to kill Moeka before killing himself.
Moeka is not seen or heard of anymore after her death. After 1% divergence was reached (true ending), Moeka can be seen at the CRT shop, working for Yuugo as an employee.
- Moeka has her own route in the new visual novel, Steins;Gate: Hiyoku Renri no Darling, which even further displays her interest in Rintarou.
- The nickname "Shining Finger" is the ultimate attack of Shining Gundam in G Gundam.
Lab Member 005.Joined in episode 6. She is recuited because she wants to see IBN 5100.