Warning: Spoilers for Bleach: A Thousand Year Blood War, part 3, episode #10!Bleach: Thousand Year Blood War has just seen the Soul Reapers lose another of their own kind, and the circumstances of that particular death are among the cruelest and most disgusting in the entire series. Even more unfortunate is that this particular Soul Reaper has been criminally underestimated and will no longer have the chance to display the abilities that made her unique.
Nemu Kurotsuchi is the lieutenant of Squad 12, serving under the command of Mayuri Kurotsuchi, its creator. Nemu is actually an artificial Soul Reaper, created using the same technologies that led to Mod Souls, or the Gigai used by Soul Reapers when entering the world of the living. A very mysterious character who is often used as a tool by Mayuri, Nemu is interesting because she displays her own personality, despite attempts to prevent her from developing independence. Nemu has a multitude of abilities, including poisons and medicine for Mayuri to use, but many of them have never been seen on screen.
Nemu's final battle made her a worthy lieutenant
Nemu proved that he always had the ability to be a lieutenant
While fighting Pernida, Mayuri had to be saved by Nemu after one of Pernida's nerves made contact with Mayuri's arm, forcing him to cut it. Nemu managed to give him some medicine that helped him recover his arm quickly, although he was unhappy with her decision to interfere as he did not explicitly ask for it. Mayuri entrusts Nemu with a coagulating agent, with which he hopes he can shut down Pernida's biological systems..
Nemu bravely crossed the dangerous battlefield and injected Pernida as ordered, but it was not enough to fully defeat Pernida. Nemu then defends Mayuri, enhancing her own abilities at the cost of increased cellular degradation. As Mayuri argues with her that she shouldn't protect him, Nemu delivers a powerful blow using part of her soul, which blows a hole through Pernida. However, Pernida is not defeated and sends Nemu into a tizzy, making contact and instantly causing her to explode in a shower of blood.
Nemu proved that she has evolved beyond her capabilities, as Mayuri always wanted; however, her evolution eventually led her to actions that would lead to her death. Mayuri mourns, although he doesn't fully understand the feeling.
Is death really the end of Mayuri's greatest creation?
Nemu was the latest in a line of experiments
Nemu was also known as Nemuri Nanago, marking her as experiment #7 in Mayuri's Nemuri Project. The only attempt by an artificial Soul Reaper to live beyond the expected age of two, Nemu was an incredible creation that was never as valued by Mayuri as perhaps he should have been. While Nemu dies during the battle with Pernida, Mayuri manages to save her brain, suggesting that perhaps all is not lost for her greatest creation.. If the medical capsule that Mayuri entered is able to keep the brain alive, it may be possible to revive Nemu somehow.
At the very least, Mayuri has all the notes and experiment data from Project Nemuri, with which he could create a new Nemu. He now knows how to overcome the cell division problem, which is what led to the failures of Nemuri #1 to #6. Mayuri will have to raise a new Nemuri for a long time, as he doesn't seem to have a safe way to quickly age her to the age Nemu was. It's hard to imagine someone like Mayuri giving up on creating the ultimate artificial life form, so going back to work on a new Nemu after this war ends seems like exactly what he would do.
Nemu was a critically underused character in the end, someone who didn't receive the respect that most of the other Soul Reaper captains and lieutenants received. She had very interesting circumstances that made her a potentially exciting character to watch, but she was so rarely able to deliver on her abilities that this final fight shows more of what she's capable of than perhaps any other. Able to modify herself and her parameters quickly, Nemu had access to superhuman strength and speed that would have come in handy in previous confrontations.
While it is tragic that Nemu was lost under such disturbing circumstances, at least the Soul Reaper died in a way that led to the defeat of his killer, which is the best one can hope for in Bleach: Thousand Year Blood War.