Characters: Mayuri, Nemu
Summary: Here's a quandary for the ages.
Pairings: None
Warnings/Spoilers: No spoilers
Timeline: No timeline needed
Author's Note: I'm confused by this too.
Disclaimer: I don't own Bleach.
Needless to say, Nemu's creation is a source of much confusion and eyebrow-raising among the denizens and the higher-ups of the Gotei Thirteen. Mayuri's dramatic announcement that he is now the father of a tall, leggy young woman with black hair and a blank expression just deepens concerns among all others.
What on Earth does he want a daughter for?
It soon becomes clear to all that Mayuri's reasons for constructing Nemu were neither altruistic nor out of the desire for parenthood when he begins including her in experiments, actually conducting experiments on her and wholesale subjecting her body to every sort of abuse he can think of, just to test her pain thresholds and her regenerative abilities. Maybe it's the fact that she never screams that keeps Mayuri coming back to inflict more pain.
If it's just a matter of needing a lab assistant, why not just create a life and not call it "daughter"? Mayuri doesn't need a daughter to assist him with his experimentation. He doesn't need a child to be his guinea pig. He can have cadavers or the Shinigami and denizens of Rukongai he coerces and strong-arms into cooperating with him for that.
If it's a matter of control, of wanting something to hurt with impunity, then why on Earth did Mayuri give Nemu the designation of "daughter"? That defeats the purpose. Most would think that Mayuri would want to distance himself as much as possible from Nemu if he wanted to inflict pain, but no; he simply gave her the designation that bound her as closely to him as humanly possible.
Mayuri shows no care for Nemu, no concern. On bad days he nearly kills her (then puts her back together, but still…) and on good days he barely notices she's there.
Why does he refer to her as his daughter?
No one in Soul Society knows.
Not even Mayuri himself.