Rubik

Rubik (ルービック Rūbikku), known as Sugarcube (角砂糖 Kakuzatō) in the anime, currently works in Security at the Chicago headquarters of the Nebula megacorporation under Cal Muybridge.

Appearance
Rubik has black hair, a long face, and black-rimmed square glasses. He always carries a jar of sugarcubes with him. Carol seems to think that Rubik has a 'black aura' enveloping him.

Personality
Rubik is a calm, expressionless man who moves between organizations and jobs as it suits him. He has a good grasp of his abilities and his competency, and believes that he could do a better job of running Nebula than his employer Muybridge could. He seems to have some insider knowledge of homunculi - at the very least, he is aware of Sham, likely due to his connections to the Runorata Family and Manfred Beriam.

He has a habit of snacking on sugar cubes.

Chronology
For an undisclosed amount of time, Rubik earned money as a regular customer of the Daily Days, selling information to both them and enemy organizations. He was particularly useful as a customer due to his involvement in multiple organizations, among them the powerful Runorata Family mafia.

Sometime in 1933, Rubik decides to abandon the information selling business after concluding that there is no possible way he can compete with the 'monstrous group of men' known as Sham, who also regularly sells information to the Daily Days and other organizations.

Sometime before December 1934, Rubik finds work as part of Security at Nebula's headquarters in Chicago. Though Muybridge says that Rubik 'formerly worked' for the Runoratas, it is not entirely clear whether he has actually 'left' the Runoratas or if he is working for Nebula on Bartolo Runorata's command. Given that the Runoratas are colluding with Nebula, the latter possibility is not out of the question.

In December, Rubik is on standby in Cal Muybridge's office while Cal chats with Gustav St. Germain, Carol, and Lua Klein. Cal eventually excuses himself and leaves his three guests in Rubik's hands, remarking that Rubik's past experience with the Runoratas might prove useful if the three have any questions over what types of mafia tricks they ought to be alert for.

Rubik introduces himself and asks that the trio follow him to the guest rooms where they had spent the previous night. As they walk, Gustav recalls that Rubik used to be one of the Daily Days' regular customers; when Rubik replies that he has no recollection of Gustav, Gustav explains that as Vice President he takes special note of the brokerage's regulars.

Gustav asks why Rubik lost contact with them, and Rubik explains his realization over Sham's monopoly on the business.

Once Rubik is finished with the three guests, he leaves the building to join several other Runorata members at an abandoned Chicago factory temporarily housing Jacuzzi's Gang. The Runoratas incapacitate Rail and seize Miria Harvent; when Nice Holystone pleads with Rubik to release Miria, Rubik assures her that once 'it' is over, they will all be released, popping a sugarcube into his mouth. Nice surrenders.

Rubik and the Runoratas return to the Nebula skyscraper with their three captives, meeting up with Bartolo, Begg Garrott, and other Runoratas. They take the elevator up to one of Nebula's conference rooms (with Rubik carrying Rail on his back), where Bartolo proceeds to interrogate Rail and Nice while Miria is kept in another room next door. Renee Parmedes Branvillier's unexpected arrival causes Rail to snap, and they set off one of their explosives and use the ensuing chaos to escape with Nice to the rooftop.

An ensuing showdown between Renee's researchers and Jacuzzi's gang (plus affiliates) occurs on the building's rooftop garden, and ends with most of Renee's researchers brutally stunned and the opposing faction fled through the back stairs. Rubik and Cal eventually visit to the rooftop to survey the damage under the light of the setting sun; where the Chairman cheerfully laughs, Rubik dolefully points out that the day's events have been nothing short of a disaster for Nebula's employees.

Cal refuses to be pessimistic, countering that at least Nebula now knows a little more about what Huey and his followers are planning. Rubik disparages his train of thought as 'pointless', finding no benefit in Nebula engaging with Huey's games. Internally, he grouses that he could do a better job than Cal as chairman (referring to his experiences alongside such leaders as Bartolo and Beriam) and wonders how nobody has yet replaced an 'idiot' like Cal.

Rubik consoles himself by snacking on sugarcubes, which he refuses to let Cal try when Cal asks for one.

Role in the Anime
Rubik is first introduced as a member of the Runoratas, holding the employees of the Daily Days at gunpoint while Runorata capo Gustavo Bagetta threatens Nicholas Wayne for information. Rubik later assists Gustavo in the kidnapping of Eve Genoard by placing a phone call to the Genoard Manor under the guise of a Daily Days employee. He is assigned to watch over Eve while Gustavo sleeps, but instead pretends to fall asleep in his chair, giving Eve the opportunity to escape. By the time Gustavo wakes up and finds Eve missing, Rubik has wrapped ropes around himself to give the impression that Eve tied him up.

It is later revealed that Rubik is actually a Daily Days employee when he shows up in The President of the Daily Days' office while Nicholas and Elean Duga are in conference with him. Rubik offers Nicholas a sugarcube, which he refuses, and then offers one to the President, whom accepts. Nicholas and Elean watch in fascination as Rubik disappears behind the President's desk, making him the only known character (at least in the anime) who knows what the President looks like. Before Rubik leaves, the President instructs him to continue keeping an eye on Eve.

Trivia

 * Rubik is only ever credited as "Sugarcube" in the 2007 anime adaptation, and even referred to as such by The President of the Daily Days. His real name is undoubtedly a reference to the puzzle Rubik's Cube.
 * In a post published on September 14, 2007 for the anime Staff Blog, scriptwriter Noboru Takagi says that Rubik was created during the trial-and-error period of the anime's development. He then remarks that Ryohgo Narita decided to retroactively add "Sugarcube" into the light novels early on; specifically, Narita wrote Rubik into Volume 10 which was published in April, a few months before the anime debuted.
 * Novel illustrator Katsumi Enami, in a July 11, 2007 post on his personal blog, writes that Sugarcube's design is anime-original and potentially the work of Kishida himself.
 * In the novels, he carries his sugarcubes in a jar. In the anime, he carries around a small Cockatoo-brand box of sugarcubes instead.
 * Rubik's voice actor in the English dub, J Paul Slavens, also voices the alchemist Pierre in Episode 07. His Japanese voice actor, Kenta Miyake, also voices Berga Gandor.