|Height||5'1" (155 cm)|
|Year||2nd year in high school|
|Light Novel||Light Novel Volume 1|
|Japanese Seiyuu||Atsumi Tanezaki|
|“||Nothing less from you, Azusagawa. Such a rascal.||”|
— Rio Futaba to Sakuta
Rio Futaba (双葉 理央, Futaba Rio) is one of the main characters of the Seishun Buta Yarou wa Bunny Girl Senpai no Yume wo Minai series, who is a second-year student at Minegahara High School. She had been in the same class as Sakuta and Yuuma during their first year and is the sole member of the Science Club.
As a result of her insecurity over her body, Rio had split into two versions of herself on July 30; one who craved attention and one who hated the fact that her body was used to obtain that attention. After both versions were able to recognize and control their own feelings, Rio became one person again.
Rio is primarily seen wearing her school uniform and her lab coat. As her feminine parts developed before her classmates, Rio possesses a voluptuous figure and a large bust, which she doesn't like.
The second Rio Futaba ties her hair in a ponytail and wears contacts instead of her usual glasses.
Rio is a stoic and blunt girl who possesses substantial knowledge in science, including chemistry and quantum physics. Before experiencing it herself, she was unwilling to believe the existence of Adolescence Syndrome, but she did acknowledge the abnormal phenomenon it induces and connects them with various scientific theories and principles. Despite her stoic nature, Rio also shows various emotions such as love, as holds affection towards Yuuma, as well as anxiousness.
Rio is implied to have experienced a form of neglect, as shown when Sakuta visits her house, she tells him her parents are usually abroad because of work. In addition, she has no siblings, which further proves that she chooses to be alone as this is her comfort zone that she unwillingly developed thanks to her lonely childhood. Although, this loneliness is what gave her the courage to approach Sakuta first when they were in the same class, as she saw him as an outcast just like her.
The second Rio Futaba behaves nearly identically to the original, but she has taken a hobby of posting risque photos on social media as a form of "self-mutilation" and to have an objective look on herself.
At some point in time, Rio's feminine body parts had developed much earlier than her classmates. Once she discovered the way some boys were ogling her, she began to hate her body and felt like "a truly filthy being".
During her first term as a first year, Rio attempted to buy some bread from a food truck, but was overwhelmed by the surrounding mob of students. Before she gave up, a student named Yuuma Kunimi handed her a chocolate cornet, which would cause her to develop feelings for him.
At some point during her time in the science club, she would come to be known for performing experiments that caused power outages as well as small fires.
Rio was in the science room when Sakuta Azusagawa asked her if it were possible for him to become invisible. She replied that the human brain can affect what one would see; the example Rio gave was that she might look small to him, but to a grade-schooler would see her as big. In response, Sakuta stated that she was definitely big under the lab coat, which greatly flustered her. Nonetheless, she connected this to the theory that the existence of something is only confirmed when it is observed, namely the theory of Schrödinger's cat. Rio went on to add that people see things the way they want to be; like how the school chooses to believe the false rumors about Sakuta. She further added that the act of observation can change the observed object, and connected this to the double-slit experiment. Before Sakuta left for work, the latter asked Rio if she was okay about Yuuma Kunimi in a relationship, to which she hesitantly replied that she was used to it.
A few days after, Rio was contacted by Sakuta at 1:40 in the morning to see if she remembered Mai Sakurajima (which she did), and then listened to Sakuta explain the growing effects of Mai's invisibility and his request for her to figure out a possible solution. She mentioned that Yuuma thought Sakuta's ability to say "thank you", "sorry" and "help me" was one of his good points, which helped to ease Sakuta. Rio then concluded that since she, Sakuta and Yuuma were able to see Mai, the source of the latter's problems could be at Minegahara High School.
The following day, Rio learned that both Sakuta and herself did not sleep last night and informed Sakuta that everyone save for him and herself may have forgotten about Mai, since Yuuma had forgotten her. Referring to their conversation about Schrödinger's cat, Rio inferred that because the students are unconsciously treating Mai's existence like air, the school had become Mai's cat in the box; the only option was to somehow change their indifference into interest. She then suggested that assuming consciousness and observation were the keys, the catalyst for the students' memory loss would have to be sleep. Unfortunately, Rio was not able to stay awake that night, and forgot about Mai the next day. It was only after Sakuta shouted a confession of love for Mai in front of the school that she regained her memories.
When June 27 was looped for the third iteration, Sakuta went to Rio for assistance. Rio speculated that the June 27 being looped was simply looking at the future from an earlier point in time. She elaborated by explaining the concept on demon Laplace's Demon; if someone were to figure out the position and momentum of every atom in the world, they could instantly calculate a future situation. After Sakuta denied being "Laplace's Demon", Rio suggested he go look for a person who acted differently after every iteration of June 27 and who retained the memories of the past time loops.
Once Tomoe Koga ceased her simulated future (thus resetting time back to June 27), Rio remarked on how Tomoe took hints to fit in with everyone and ended up being able to read the future. In response to Sakuta's curiosity as to why he was the only one who experienced Tomoe's time loops, Rio suggested that he and Koga synchronized as they had became entangled in a manner like quantum entanglement. After noting the latter happened after two particles collided, Rio asked if he and Tomoe delivered any impact to each other. Sakuta simply replied that they kicked each other's butts. In response, Rio asked Sakuta to volunteer his butt to recreate such a phenomenon, much to Sakuta's disapproval.
Sometime before summer break, Rio created a social media account out of the desire to get someone's attention. She began posting lewd photos of herself and found salvation in receiving reactions, but in the end she was unable to get rid of her self-disgust. The resulting stress from her contradictory methods and results separated herself into two Rios: one that wanted attention and the other who could not forgive that her body was used to obtain it.
On July 30, the duplicate Rio began living at her home, which forced Rio to stay at a net cafe. At some point, the second Rio began posting numerous risque photos on social media.
On August 2, the second Rio was approached by Sakuta, who informed her of his encounter with a girl named Shoko Makinohara. The clone suggested that she could be a look-alike, as people say there were three people with the same face in the world. While leaving the library, they learned of an upcoming fireworks festival; Sakuta remarked on how she should have worn a yukata for Yuuma last year, before leaving for work.
Later that night, the original Rio was approached by Sakuta and Mai at the net cafe she was staying at. After informing them of her predicament, she took Sakuta's offer to stay at his apartment. While taking a bath, she connected her problems with quantum teleportation by comparing her clone to one's perception of a blueprint with information on how to construct herself. Rio further theorized with Sakuta (who was outside the bathroom door) that the clone was a copy of her mind.
The next morning on August 3, Futaba had breakfast with Sakuta, Mai and Kaede and noted that it was her first breakfast with other people. Upon noticing Shoko arrive at the door, Rio was mildly surprised to see that she was real. She would later help Kaede and Shoko with some schoolwork after Sakuta left.
Meanwhile, the other Rio was outside the school gym spectating Yuuma playing a basketball game. Sakuta, who met up with her shortly after, asked the other Rio why she became infatuated with Yuuma. After detailing how she fell in love, Sakuta revealed to her that another Rio was staying at his apartment, which explained to her why he acted strangely over the phone. The second Rio learned that the other Rio had connected their situation to quantum entanglement (which the other Rio also did) and of her theory about them being two copies of the same mind. However, upon hearing that the other Rio could not think of a possible cause, the second Rio questioned Sakuta for believing "such a lie". Nonetheless, the second Rio revealed she had a clue to figure out the cause, before leaving to do club activities.
Rio made curry for everyone in Sakuta's apartment and then went to take a bath. While bathing, she disclosed to Sakuta the circumstances over posting photos of herself on the internet and concluded that the stress from such circumstances is what split herself into two people.
The other Rio boarded the train with Sakuta and revealed to him that she took those photos as a means to get an objective view of herself and as a method of "self-mutilation", as she hated who she was. Before getting off the train, she told Sakuta to give up on one of the two Rios, reasoning that the world did not need two Rio Futabas. After Sakuta returned home and asked her if she thought of a way to become one person again, Rio doubted that possibility, as they were currently doing separate things and gaining different experiences.
At school on August 5, the other Rio asked Sakuta for his decision, to which he responded that was something for her to decide. They noticed Yuuma run up to the window gasping for air, which the other Rio obliged to by fanning him.
A week later at the train station, the other Rio and Sakuta were disturbed upon seeing on the former's phone that a person online had deduced from the photos that the other Rio was from Minegahara High and had threatened to expose her unless they met up with each other. Sakuta promptly replies to the individual by threatening to call the police. Still bothered, the other Rio urged Sakuta to delete her social media account. Later arriving in front of her home, the other Rio asked Sakuta to stay with her for the night. There, she told him how she had gotten used to living alone before meeting him and Yuuma, and was worried about losing their attention after they both got girlfriends. Sakuta assured her that they would still be friends, but after stating that she didn't understand Yuuma, he called the latter to meet up at Honkugenuma Station immediately, much to the other Rio's surprise. After she watched a mild confrontation between Yuuma and Sakuta, the other Rio began to cry as she realized she was never alone. As the three spent the night at the beach playing with sparklers, they announced that they would attend the upcoming fireworks festival.
The following morning, the other Rio asked Sakuta to take care of her other self. Once Sakuta got home, he gave Rio her phone and informed her that he had deleted her social media account. However, when he was gone, Rio was disturbed to find a photo of her other self spending time with Sakuta and Yuuma, and went to sit alone at the school. Soon approached by Sakuta, she lamented that the other Rio was faring far better than herself, thus making her obsolete. Sakuta declared her statement completely wrong and announced they would meet up with Yuuma at Kugenuma-Kaigan station on August 19, before falling unconscious. Once Sakuta recovered at the hospital, Rio was told that it was fine if she hated herself; in response, Rio remarked that Sakuta's blatant advice was somehow a relief. She asked Sakuta if she could go to the fireworks festival with them, but was directed to call and ask someone else. After calling her other self, she disappeared on the spot, having become one person again. On the other line of the phone, Rio advised Sakuta not to be late.
While watching the fireworks festival, on August 19, Rio confessed her feelings to Yuuma, but before he could reply, Rio claimed that she already knew the answer. She then told him to make up with his girlfriend, before wiping away her tears to watch the fireworks.
Rio was consulted by Sakuta for a possible solution to the body switch between Nodoka Toyohama and Mai Sakurajima. Considering that Adolescence Syndrome may have stemmed from Nodoka's inferiority complex towards Mai, Rio speculated that becoming a popular idol should reverse its effects. Upon learning that Nodoka and Mai regained their bodies, Rio proposed the occurrence was some form of quantum teleportation born from Nodoka's jealousy of her sister and suggested Mai was jealous of Nodoka as well.
When Sakuta consulted Rio about the letter he received from the older Shoko Makinohara, Rio eventually decided he was too tedious to deal with and summoned Mai to deal with him via text, before leaving the science room.
- Main article: Adolescence Syndrome
Rio's effect from Adolescence Syndrome was that she split into two versions of herself; one who wanted attention by posting lewd photos of herself and another who didn't like having her body used to get attention.
Rio regards Sakuta as a close friend she cares about. Although not much is known about their relationship and their past, she is willing to constantly work on and research the strange occurrences that happen with him. She was one of the few people to not shun him after Kaede's incident with Adolescence Syndrome. Rio views Sakuta and Yuuma as her only friends and admitted that she was worried that Sakuta would ignore her after he started a relationship with Mai Sakurajima. She trusts him enough to stay in her house overnight with her and accepted his offer to stay at his apartment when the duplicate Rio was created. Whenever Sakuta has a question regarding an event with Adolescence Syndrome, he usually stops by the school lab where Rio is.
Upon learning that Older Shoko Makinohara's existence is only possible due to Sakuta's death, she spends countless hours trying to understand the situation and prevent it while saving Shoko. Unaware of Sakuta's experiences during this time, she cannot find a solution that would save both of them. In an alternate timeline where Mai died instead of Sakuta, she offers for Sakuta to stay at her place to keep him out of public eye. When Sakuta returns after resolving the situation, she breaks down and admits how scared she was of losing him.
After Yuuma gave her a bag of bread when she was unable to, Rio developed a crush on him, which she was insecure about. When Yuuma greeted her on a train, Rio experienced feelings of happiness but later bemoaned the fact that she was that excited over a simple greeting.
After she became one person again after she was affected by Adolescence Syndrome, she confessed her feelings to Yuuma on the fireworks festival, but before he could reply, she claimed that she already knew and added that she would cry if he said anything, implying that Yuuma did not reciprocate her feelings.