Survival of the Fittest (適者生存, Tekisha Seizon) is the 9th episode to the Munou na Nana (Anime).
Once again managing to throw Kyouka off her trail, a surprise confrontation, by Michiru throws Nana off guard. This confrontation with Michiru turns out to be a ruse set up by a shape shifter named Jin who wants to strike a deal with Nana.
In Kyouya search for evidence on Nana, he doesn't find anything. The item in question was Kirara's cell phone and Nana was relieved that she wasn't found out. Nana had three plans sorted out and out of the three she went with the 3rd, which was of high risk, but she went with it and it worked. Michiru then speaks in defense of Nana calling out Kyouya for being inconsiderate by accusing Nana of murder. Begrudgingly, Kyouya apologizes and after Nana hears the voice of Kirara from afar, the two shake hands in what seems to be good will, but Kyouya still notes something is off.
Afterward, during the night just outside the dorms, Nana contemplates about disposing the poison, and how to proceed there after. Just then, Michiru approaches Nana and when asked why she's sitting there, Nana answers she's on guard against the Enemies of Humanity. Impressed by this, Michiru praises Nana and volunteers to stand watch with her. Accepting, Michiru's offer Nana doses off for a bit until, she's caught by surprise when Michiru holds a box cutter knife to her neck. Michiru with a cold look on her face, demands to know why Nana didn't use her Mind Reading Talent to catch her in the act. This sudden confrontation leads to a brief interrogation about Nana's Talent, until Nana is able to disarm Michiru. To her delight, Michiru manages to deflect any argument Nana gives that would try and implicate her of any wrong doing in that situation. In the end, two students spot Michiru and ask if she's alright, whereas, she returns to her sweet persona and informs them that she's fine. Returning to the Dorm, Michiru says that she'll see Nana again tomorrow and also calls Nana her "friend", which infuriates her.
The next day in school, Michiru presents Nana with a small box claiming it's a present for the class rep. On the other hand, Nana doesn't accept it, which is ok with Michiru, as she'll have plenty of other chances to give her the present. The truth to Michiru wanting to give her present is to catch Nana off guard which would expose her "True Talent". Eventually, Nana opens Michiru's present in front of the entire class, but gets it wrong. Before Michiru could take advantage of the discrepancy, Nana reveals the phrase "I love Nana-shan". Kyouya then points out the paper with that phrase written on it attached to Michiru's back. Although he openly asks who could have put the paper on Michiru, Kyouya drops it after his blunder the night before.
By the cliff side, Nana confronts Michiru and outs her as a fake. The fake confirms this and introduces himself as Jin Tachibana and proposes a deal with her. Taking Nana to a untold location, Jin assures Nana that the real Michiru is fine. At the location, the two talk about how Jin has many cards to play against Nana as he has preponderant evidence that he use against her. He also states that the corpses used by Yuuka's Necromancy were his former friends and that the cat Kyouka fed was himself. The one that Nana rescued from the drain that one time, was the real cat. Meanwhile, Kyouka studies various poisons that Nana could have used to kill Kaori with. Back to Jin and Nana, Jin discloses how 5 years ago all of his fellow classmates started to kill each other. How Jin managed to survive was by transforming into an animal and by doing this was written off as dying heroically against the Enemies of Humanity. Jin learned this when he met with his grandmother who told him of that fact. With no where else to go, Jin returned to the island. Eventually, Jin learns of Nana, which lead him to propose the deal to her. On the other hand, Nana has no interest in said deal as she secretly poisoned his coffee that he served the two of them. Shown to have the upper hand, Nana uses her phone to mark another successful target dealt with, but is accosted by her classmates. However, this was all an illusion created by Jin, who turns can not only copy appearances, but also their Talents as well. From this revelation, Nana believes that she found the true Enemy of Humanity.