Neural Nano-Interface

Neural Nano-Interface is a human brain augmentation which allows it to function as a supercomputer.

Description
A common technology used by humans from the World of 2138 in Overlord series. It involves injecting a syringe of nano machines directly into the subject's arm, allowing their brain or mind to function like a computer— a super high-performance personal computer.

When starting it up, several windows would popped up within the subject's line of sight, showing his/her the information flowing into the processor within their brain. In a way, the subject can then begin operating the CPU. Afterwards, the subject's cranial CPU will read the electrical impulses of their synapses — in other words, it was thought controlled— and converted it into data.

Additionally, the subject's thoughts is able to reach into their supercomputer through the medium of the cable. As a result, he/she can manipulate an invisible console to turn on the television, change channels, and so on via the use of hand gestures alone. Despite operating the console window floating near their hand, the subject can still opened several new windows nearby. He/she will then bring either one of them near his/her hand before touching it to start a particular program.

However, it requires a dosage of syringe to restore nano machines back to power required before operating programs like YGGDRASIL, a DMMO-RPG. If not done so right away and started the program anyways, then he/she will be booted out halfway during the game because of an error about it. Upon fully using the neural nano-interface, the subject's cerebral nano machines began their computations, disrupting one's field of vision and taking control of their voluntary nervous system.

Risks
The interface was essential for daily life, but sometimes they were used in criminal activities as well. A well-versed hacker could utilize the brains of others as a springboard to commit crimes.

Although it was supposed to be a full-face helmet, the camera mounted on the outside would transmit its video signal directly to the subject's brain, so his/her field of vision can still be clear. Thus, special helmets were designed to include a system that would automatically record everything which went on in the virtual world. Moreover, it would retain footage for a month, automatically deleting it after that. These monthly records functioned to record the user's actions to prove his/her innocence, even if the wearer was implicated in a crime.

One could say this was the safety net of the computing world. In contrast, not having one of these greatly increased the chances that one might be charged when involved in a crime, so only a handful of people chose not to wear them.

Requirement
In order for full operational neural connection and before beginning a game such as YGGDRASIL, nano machines needed to be replenished into the subject's system. How to replenish it is through dosages of cerebral nano machines which could be bought in common clinics.

On the other hand, the subject could cheaply exchange an old one for a new one at a clinic. If the subject broke it however, then the replacement would be very expensive to buy. Therefore, the subject must treat it carefully, in order not to waste money needlessly.

Trivia

 * In the Overlord Twitter Side Story, it's said that the neural nano-interface connects the brain directly to something called the Megacon.
 * People from the World of 2138 wear the VR Helmet not just because it was mandated by computer laws, but did so in order to protect themselves.