"Sanae and Ritsu-kun share a name. Ritsu-kun is Sanae's sacrifice"Sanae Sagan (目 沙苗 Sagan Sanae) was the younger sister of Nagisa Sagan. She was Ritsu Minami's Fighter, sharing the name "Endless" with him.
Sanae died when she was 13 years old by drowning in a pond outside of Seven Voices Academy. Her death is implied to be suspicious.
Sanae is first shown at the start of the flashback chapters, which span chapters 126-127 and focus on Seven Voices Academy in the past. It's not known how far in the past the flashbacks take places, but it's assumed to be at least 20 years before the start of the series. The events of the flashback are narrated by Nagisa Sagan as she speaks to Natsuo Sagan.
The flashbacks start when Sanae is 13, with her sister and Ritsu Minami being 15 years old. While they're third-year junior high-school students, Sanae is a first year. The three of them, among others, attend Seven Voices Academy and are shown to have attended the same school since they were young. Nagisa, Ritsu, and Sanae are all part of the biology club at the school, headed by Masaki Aoyagi, with his teaching assistant, Akio Sugou.
The chapters begin by Nagisa insisting that Ritsu become part of the biotrope club, which she and Sanae are in. Ritsu doesn't seem interested, and Sanae doesn't seem to mind, even when Ritsu acts disrespectfully towards both her and her sister.
During the club, Akio Sugou comes in and Ritsu becomes involved in arguing with her over a conversation they had earlier, while Sanae watches. Nagisa tries to comfort her by saying that Sanae is the only person who matches perfectly with Ritsu, and it's revealed that Sanae and Ritsu share a name, Endless, and it's written on the inside of both of their right wrists. However, Sanae seems to recognize what her sister doesn't- that Ritsu has fallen in love with the much older Akio.
Afterwards, Nagisa and Sanae go out to the pond outside the Academy in search for things for their biotrope. Ritsu interrupts them, and Sanae abruptly sends Nagisa off by telling her that she'd forgotten something in the classroom. While in the classroom, Nagisa notes to classmates that Sanae cannot swim, so Nagisa doesn't want her going into the pond.
Sanae confronts Ritsu and her sweet personality collaspes around her. She mocks Ritsu and calls Akio 'a hag without a name'. She comments that she likes to trap things in her biotropes and control their environment so they can't run away, and she makes Nagisa build the biotropes for her. Soon enough, she reveals to Ritsu that she's stolen Akio's engagement ring and shows it to him while mocking him for falling for her.
Nagisa also recounts a time when they were smaller. Nagisa, Ritsu, and Sanae were childhood friends and even attended elementary school together. It's shown that Ritsu has never cared for Sanae's well-being, even choosing to ignore her when she got hurt while they were kids, seeing her as more of a bother or an annoyance.
Ritsu immediately gets angry with Sanae for stealing Akio's ring and yells are her, saying, "You are the worst." This causes Sanae to, at some point, drop the ring into the pond. Ritsu witnesses this and walks away from her.
Nagisa comments that that night Sanae's body was found in the pond. During the flashback, however, the circumstances surrounding her death seem strange, including the fact that the water Sanae was in while she was looking for the ring was only knee-deep.
At first glance, Sanae seems sweet and kind and prefers to trail behind her older sister. She lets Nagisa do work for her and doesn't seem to protest much. Initially, she appears to be well-mannered and soft-spoken. Nagisa clearly sees her this way and does not seem to witness her true colors. Sanae even makes sure to send Nagisa away when she confronts Ritsu and mocks him.
When Nagisa is away, however, Sanae changes into a completely different person. She openly mocks and makes fun of Ritsu and insults Akio when talking to him. She took an item that Akio had of sentimental value for the sole purpose of making Ritsu upset. She also seems to display some need for control, as shown when she talks about her biotropes and forcibly trapping small animals with the intent to control them.
However, this doesn't seem to be all there is to her. When Ritsu yells at her and tells her to give the ring back, she becomes visibly upset and insists that she was going to give it back anyways. When she drops the ring, she does go after it, though it's unclear whether she did this to repair her relationship with Ritsu or because she actually wanted to give the ring back to Akio.
While most of her smiles seem sarcastic and fake, she does appear to have a soft side and some morals. It's also important to note that she was only 13 at the time all this transpired.
Nagisa is Sanae's older sister by two years, making her fifteen when the events in the flashbacks transpired. Nagisa's attachment to Sanae was strong, and it's shown during the flashback that all Nagisa wanted to do was protect her little sister. Nagisa did what Sanae asked of her without question, even if it meant wading into a pond to catch things for the biotropes. Nagisa was the one to defend Sanae when Ritsu treated her coldly, and when they were elementary school aged, Nagisa is the one to help Sanae when she's injured from falling. Nagisa remarks to Natsuo Sagan that Sanae was at the center of her world. Nagisa also did not seem to be aware of Sanae's true personality. Nagisa appeared energetic and happy around her little sister, and clearly cared for her a lot.
Seven Saotome once says that Nagisa has a "sister complex" and while it does seem that Nagisa is still obsessive over her sister after her death, Nagisa did not appear to have harbored any sort of incestuous feelings towards her little sister.
Nagisa was clearly deeply affected after her sister's death. It seems to have ruined her childhood friendship with Ritsu Minami, and she has hated Soubi Agatsuma for all his life because of the connection with his mother, Akio Sugou. Over the years, her personality has changed and Nagisa has become spiteful and angry, and it's implied that she's still suffering over her sister's death. She does keep a photo of Sanae in her apartment. She also modeled Youji Sagan after Sanae, leading to Youji becoming her favorite Zero.
Sanae and Ritsu's relationship was complicated. They were early childhood friends, though Ritsu never seemed to care much for Sanae. They are a bonded pair, sharing the name 'Endless'. Ritsu does not treat Sanae well in the chapters where she's shown, but his treatment of her is nowhere near that of his later treatment of Soubi Agatsuma. He mostly appears irritated and annoyed by her, though when Sanae shows her true colors and mocks him, they get into an argument about Sanae's actions. Ritsu remarks that Sanae is "the worst", implying that this isn't the first time that Sanae has done something so mean-spirited. Ritsu doesn't seem to like being around Sanae much. When Ritsu confronts Akio about his feelings, Ritsu tells her that "Sanae has nothing to do with this" when Akio tells him that he's better suited for his Fighter.
It's unclear how Ritsu reacted to her death. Nagisa Sagan does seem to blame him partially for her death, as Ritsu was the last person to speak to her and see her alive, and because of the fact that he left her in the pond when he knew she couldn't swim. Ritsu doesn't talk about Sanae much, the only indication of her is when Soubi Agatsuma insists that Ritsu take him on as a Fighter. Ritsu tells him that he already has a Fighter, to which Soubi replies by pointing out that she's dead. It's unclear how much Soubi knows of Ritsu's relationship with Sanae or even about the events having to do with his mother and Sanae's death.
While Sanae does not directly interact with Akio, she does seem to be jealous of her and Ritsu's romantic feelings for her. This leads her to stealing Akio's ring. From the way Akio refers to her ('Sagan-san'), they weren't close, though Akio does tell Ritsu to 'cherish her' and calls Sanae a 'precious Sentouki'. Akio also doesn't seem to know that it was Sanae who took her ring, as she assumes that she just misplaced or lost it.
Other Students Edit
In the biology club, Sanae interacts with other students, including Misaki Imou and Seimei Nowaki. Misaki refers to Sanae as 'Sanae-chan' and they seem to be friends. Misaki also comments to Seimei Nowaki that Nagisa is the 'only one who doesn't know', prompting Seimei Nowaki to respond with 'this is slavery', referring to the fact that Sanae makes Nagisa build her biotropes and that Sanae isn't what Nagisa thinks she is.
- Sanae's name means 'seedling'.
- At the end of chapter 125, a girl is shown with long hair when Nagisa is talking about the person at the center of her world. When Sanae died, she had short hair. It's unclear if this was an artist mistake or if it holds some value.
- The circumstances surrounding Sanae's death are unclear, as she was wading in knee-high water. It's possible that she fell into the deep end, but fans speculate that someone pushed her, given the narration while she's falling.
- Sanae's death seems to be the biggest reason why Nagisa went into biology and subsequently created the Zero series.
- It's unclear how much Youji Sagan resembles Sanae, but he was supposedly created in her image.