The twist isn't all too interesting to me. I do still like the manga itself because it's another one of Agasa Reiji's works. You should check out the translations of his other stuff on MangaDex.
As for the translation itself, it's okay. It keeps the story beats intact. However, I read the raws on the official Shonen Jump site a few months ago.
On page 21, not only is being a nurse Nagisa's calling, she's been "taking care of family since I was little, so it only felt natural." In retrospect, the entire page is about her sister and how devoted Nagisa is to her. The translation on page 43 especially doesn't really do the historical allusions behind Nagisa's motivations justice.
I'm going to put the wikipedia article for what I'm talking about,
Minamata disease, for other people's reference. What I'll talk about is from my own memory and might not match up with what wikipedia and more reliable sources might say. So, seaside towns got poisoned by mercury dumped into the ocean for decades by an extremely unethical company. This included women who were pregnant or would be. Their children absorbed the mercury in their mothers' bodies and were born with severe physical deformations and mental disabilities. The appearance of and mannerisms of Nagisa's older sister is vaguely similar to these symptoms.
Now, my personal translation of what Nagisa says on page 43 goes as this: "Big sister is my goddess. Because she took all of it, I was able to be born this healthy. That's what my mom told me." I find this eerily similar to what many families with children born with the effects of mercury poisoning have said. Mercury stays in the body for a long time. This fact meant that because of the extreme amounts of mercury the people of Minamata and other towns were exposed to, they would die from slow and painful illness.
However, expectant mothers managed to accidentally avoid this in a way. As stated before, most of the mercury in their bodies went to their babies instead. Since the mercury in the mothers went out in one child, the later ones would be born healthier and more normal. Families would then feel that their "treasure child" took away the brunt of the poisoning and saved the rest of them.
From this, you can see that page 43 alone reveals a lot about Nagisa and her sister's backstory. Their mom had a toxic build-up of some substance in her body, but unknowingly expelled it throught the birth of her eldest daughter. Upon realizing what happened, she considered her her "treasure child" and taught her next daughter, Nagisa, to think the same. Nagisa grew up taking care of her sister and adoring her. She was motivated into becoming a nurse to help her sister better. Nagisa's love, however, became twisted and escalated into literal sibling worship. All she wants is what her sister wants. That, you know, led to the events of this story.
With all of this in consideration, I guess the part I like the most is how the story echoes a real-life tragedy. Due to an past incident much like Minamata disease, Nagisa and her sister are caught up in intense, equal amounts of love and suffering, and they pull protag into it too.
