Elsewhere I saw a theory I liked, I don't know if you guys discussed it here yet: Mayuri called Nemu "Nemuri Nanagō" (the seventh Nemuri), indicating she is not his first experience, and he seems very adamant in stopping her from growing, of even doing anything without his permission. That brings us to Shutara, whom Mayuri seems to resent and does have some physical resemblance to Nemu. Perhaps she was his first experience? And she "outgrew" her creator, became "superior" to Mayuri — that would be the reason why he doesn't like her and is so controlling of Nemu: he doesn't want another Shutara situation in his hands, he doesn't want Nemu to surpass him. If she is actually the seventh experience, he might as well have discarded/killed all the previous ones when they started to act outside of his orders and were close to surpass him. (Or he might have simply have modeled Nemu after Shutara, but I like the other idea better.)
Do you mean experiment? I'm sure Kubo will go forever without saying anything about it, then when no one cares he'll bring it up.
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Originally Posted by Sidewinder
While it is very reminiscent of a lot of journey trainer fics, it held my attention. It stands out among a lot of the other fics I've read lately and I'm excited to continue the story.