|Spoiler Alert: This article or section contains details about plotlines not covered in the anime. Do not proceed unless you wish to be spoiled. |
The Seal of the Right Eye (右眼の封印, Migime no Fūin?) is a seal that prevents or discourages the people of Underworld from breaking any rules that are set upon them, including laws, social norms, or any instruction imposed on them by someone they may consider higher than themselves, like a parent or god.
Knowledge of this Seal, or even the fact there is a restriction on the wills of people to begin with, is not commonly known, though there are some people that show signs of awareness of the Seal, including Miss Azurika, who claimed that she was unable to break the Seal which Eugeo did.
The Seal was likely created by a person from a large company monopolising the domestic defense industry or a foreign arms manufacturer who infiltrated Rath to sabotage their project. However, as the person only delayed the project by implanting such an inhibitor into the system, instead of just destroying the Light Cube Cluster, it is likely that the person's true goal is only to slow the project down in preparation for stealing Project Alicization's experimentation results, as well as the Light Cube Cluster, which houses the Artificial Fluctlights themselves, for their own gains.
The Seal works by inducing great pain onto a human's right eye whenever they even attempt to think about questioning or breaking any rules that they believe have authority, to dissuade them from questioning or acting out against an imposed rule. If a person continues to think about the rules and even decides to attempt to break them, the Seal paralyzes their body, with the words "SYSTEM ALERT" (in English) appearing on their right eye (Eugeo's case seemed to also have "CODE 871" appended to the System Alert), thus preventing them from continuing to take action. However, the Seal's effect can be avoided through exploiting loopholes in the rules that the residents regard as authority, and thus some residents, especially nobles, continuously search for such loopholes to abuse for their desires.
This "Seal" is not, however, absolute, as both Eugeo and Alice seemed to be able to break free from the Seal's hold by overwhelming it with willpower when extreme situations provoke them to greatly question their sense of judgement. If the person manages to overwhelm the Seal, this leads to the destruction of the eye, after which the person is able to freely break the rules imposed on them, if it is within their will to do so, while the Fluctlights who lack the willpower to overpower the Seal but cannot bring themselves to stop thinking about breaking them, like in Raios's case, may collapse from the pressure, even if their avatars do still have Life remaining.