USER-E21, formerly known as MD14, serves as i026's self-destructive alter ego, akin to i124, but with a distinct manifestation. Unlike i124, USER-E21 does not engage in self-harm through physical injury but rather through starvation and severe food restriction as a coping mechanism.

USER-E21 struggles with an eating disorder, specifically anorexia nervosa, and possibly ARFID. At one point, they contended with both anorexia nervosa and bulimia. A 19-year-old with hikikomori tendencies, USER-E21 spends their days in front of a computer, frequenting eating disorder websites and challenging themselves to remain in their room as much as possible to avoid eating. They prefer to explore these websites late at night, where they feel a sense of nostalgia for the late 2000s and early 2010s era of such sites, finding the 2020s versions toxic and overly restrictive.

USER-E21 expresses their vulnerabilities through a fabricated persona, maintaining a degree of anonymity but not fully concealing their true identity, reserving their main identity as i026. Their method of restriction involves consuming Mountain Dew, Monster Energy drinks, or other sodas, as well as drinking chocolate milk two to three times a day.