Neural Nano-Interface

Neural Nano-Interface is a human brain augmentation which allows it to function as a supercomputer. This interface is used to play DMMO-RPGs by inhabitants in the World of 2138.

Background
According to the Web Novel, this system was born in the year 2079. Yet by the year of 2126 however, it was eventually released by a local Japanese producer and was coined as a sensory-based MMO.

Initially, the first aim of creating this system was for sake of it being used by the military. Afterward, it would then be used again in terms of development for the field of medicine, but the cost was high. The system's development was later simplified after 10 years and now every home has it. Although techniques created by net shops and tourist sites were used to lower the development costs, it still took 15 years before the first DMMO-RPG was born.

Description
A common technology used by humans from the World of 2138 in the Overlord series. It involves injecting a syringe of nanomachines 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 pop 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. Afterward, 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 open 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 from the syringe to restore nanomachines back to the 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 nanomachines 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 at times though, they were used in criminal activities as well. For instance, there happens to be a well-versed hacker who 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, nanomachines needed to be replenished into the subject's system. How to replenish it is through dosages of cerebral nanomachines 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.