Hajime is an amnesiac and a gluttonous girl who eats a lot and often. She spends most of her time at the Nowhere Café.
She suffers from memory loss. At first, she seems ordinary, but her minimum is revealed to be enhanced speed, strength, and regeneration. It is not explained how she activates her minimum until the second season (Re: Hamatora).
It is later revealed that she was an abandoned child taken in by the Minimum Agency. She was chosen as a lab rat named ''Success Number 0-1'."
Nice found her while he was exploring the Facultas Facility. When he realized she was starving, he gave her a hamburger; this is why Hajime loves hamburgers. After that, Nice named her "Hajime" when she said she didn't have a name. Nice took her under his wing.
It is also revealed that Hajime's minimum is the Nihilist Minimum.
Her Nihilist Minimum, which is triggered by despair, has the power to negate other Minimums. Also, if Minimum Holders are in contact with her for an extended amount of time, their own Minimum will grow weaker progressively.
This explains why the people around her start losing their Minimums.