That was, until she encountered a new kind of being from outside of the body: the superhero Ryan Choi, better known as the Atom. Setting out alongside U-1146 and the Atom to help the body fight off an infection of the 'Doomsday Virus', AE3803 wound up becoming temporarily infected herself. In a moment that shocked and encouraged her friends and allies, she was able to fight off the infection and seemingly return to normal, taking a more direct part than ever before in the body's healing from illness by sharing her story with the T-cells and Brain Cell.

Once everything settled down, however, she acted on impulse. With how strange and incredible everything had been, she had to know more—especially since the words of the Atom and his friends revealed how much more there was outside the body, and how little time she would have within it, relative to their experience. Brought from microscopic size to human scale by the interactions of the Atom's signature Bio-Belt and new lens technology produced by the Earthshine Company, AE3803 found herself a cell in the world of humanity.

After several weeks of examination and work to be legally integrated into Japanese society, the newly renamed Tenjō Mihare set out in response to an online job posting in the hopes of finding employment in a familiar area: delivering food. Exactly why this restaurant "Ucchan" was seeking a delivery person with experience acting as a courier or delivery-person in an environment where property-destroying battles were commonplace was in question when you considered Nerima's longstanding reputation as a quiet place, as was the way people reacted when she said she'd walk to the interview—after all, it was only 23 kilometers away!

• Enhancement: since recovering from Doomsday Virus infection, Mihare possesses a number of innate qualities that bring her above human norms.
  • Enhanced Durability: Mihare's resistance to injury is sufficient to withstand collisions with stationary objects at her top speed, walk off electrical shocks that would be otherwise debilitating, and suffer little more than scrapes from expertly sharpened mundane blades.
  • Enhanced Healing: Mihare's organelles and cell walls heal at a much faster rate than human norms, including regenerating missing portions over time.
  • Enhanced Strength: easily capable of hefting 200 kg over one shoulder, Mihare's strength far exceeds human norms.
  • Functional Immortality: while she does seem to be physically maturing at a normative rate, there is no evidence that Mihare is aging in a normative manner.
• Linguistics: Mihare is a native Japanese speaker, and has recently begun studying English.
• Macroscopic Cell: as a human cell originating in a pocket dimension where individual cells and groups thereof were represented as anthropomorphized beings, Mihare lacks the normative cellular makeup of organic life. Her body's structure maps to that of a human, but is composed of organelles and cell walls instead of internal organs and tissues.
• Superhuman Speed: as a former Red Blood Cell, Mihare's innate ability to quickly move around the body while carrying oxygen has translated into superhuman speed in the human world. Under normal conditions, her top speed is approximately 195 km/h.
• Transformation: when sufficiently enraged or experiencing other forms of extreme mental distress, the lingering effects of her past Doomsday Virus infection causes Mihare to transform into a mutated form with superhuman strength and durability even relative to her base form, along with crystalline bone spurs projecting from her joints that are capable of piercing through stone and steel.