Yui Kiriyama/Story Plot

Hito Random arc
On a night that should have been like any other, Yui awakens to find herself in an unfamiliar room. Upon inspecting her new environment, Yui realizes she is not only in the room of her abhorrent admirer, Aoki, she's in his body. Horrified, Yui hides under the bed sheets only to suddenly find herself back in her own room and body.

The next day, Yui and Aoki discover that they experienced the same bizarre phenomenon and decide to inform their friends. However, the rest of the Cultural Research Club are reluctant to believe their story and Yui begins to have her own doubts. After Taichi and Iori swap bodies, however, Yui and the others are convinced of the phenomenon.

The following day, to Yui's distress, she is once again swapped into Aoki's body and spends much of the morning waiting with the others for the switch to wear off. Later, Yui and the rest of the club encounter the mysterious Heartseed who takes control of their club advisor, Gotou to speak with them. Heartseed reveals that he is behind the phenomenon and that the Cultural members will continue switching bodies at random until he is sufficiently entertained. After a defiant Inaba is shoved away by Heartseed, Yui attacks her mysterious tormentor but he effortlessly blocks all of her strikes before tossing her to the ground. She and the rest of the club can only watch as Heartseed takes his leave.

Realizing how hopeless their situation is, the group decide to establish rules to ensure no one else learns of the bizarre phenomenon and so they can continue living as normally as possible. A week later, everyone meets at Inaba's house where Yui and the others confess to having failed to obey their rules, much to Inaba's frustration. Yui takes the opportunity to ask Iori why she lives alone and is horrified to learn Iori is completely unconcerned about household intruders. Returning home, Iori switches bodies with Aoki and is amazed by how tall he is. Iori approaches Yui but, strangely, the petite karate girl shirks away, claiming that she's wary of Iori because she's in Aoki's body.

The next day, after a series of switches, Aoki, due to his experiences while controlling Yui's body, suspects that she is afraid of men. Distressed, Yui flees the room, confirming Aoki's suspicions. Inaba pursues and calms Yui down before walking her home. Aoki would later call Yui several times, profusely apologizing for his insensitivity.

That night, Yui lays in bed crying when suddenly, she switches bodies with Taichi. She immediately calls Taichi, telling him not to worry about her, but Taichi requests they talk in person. Meeting at a park in the dead of night, Yui reveals that she suffers from androphobia, which she developed after nearly being raped in junior high. Despite being a martial arts expert, Yui felt powerless and has been terrified of men ever since. Taichi demands she let him help her and Yui reluctantly agrees. Claiming he knows a flawless technique that will neutralize any man, Taichi (while in Yui's body), punts Yui (in Taichi's body) in the crotch. Yui falls to the ground, writhing in pain only to suddenly return to her own body, leaving Taichi with the pain. At that moment, Yui notices someone approaching and, not wanting to raise unwanted questions, flees with Taichi, but she is forced to help him to his feet as he is in too much agony to move. Having escaped, Taichi compliments Yui on having been able to touch him despite her androphobia and Yui thanks Taichi for his help, her confidence restored thanks to her newly learnt weapon against men.

Later, at Aoki's request, Yui meets with him in private and Aoki confesses his love to her. However, Yui turns him down, stating that she is still not ready to start a relationship with a boy. Aoki understands, but remains hopeful that she will one day return his feelings.

When Iori is left critically injured at a hospital due to Heartseed's intervention, Yui is traumatized, feeling useless for not being able to protect her. Suddenly, Heartseed appears himself and announces that the group can save Iori, but only if one of them exchanges minds with her, allowing their soul to die with her body. Yui is further distressed when Taichi recklessly expresses his desire to be sacrificed. When Aoki switches bodies with Iori to inform her of her situation, Yui breaks down completely, crying tears of guilt and sorrow. Iori would later speak with everyone individually one last time before allowing herself to die with her own body. However, to everyone's surprise and relief, Iori survives her ordeal, Heartseed claiming that she was never in any real danger. Yui later helps throw Iori a welcome back party upon her return to school.

Kizu Random arc
With normality returned to the Student Cultural Club, Yui and the others enjoy a period of peace, that is, until Yui returns to the clubroom with Aoki to find Inaba seducing Taichi. Freaking out, Yui demands the two get off each other and abruptly smashes the club table in half. Aoki asks what's gotten into Yui and she seemingly snaps back to reality, confused. Iori enters the room and rushes to Yui's side, tending to her wounded hand. Returning home that day with Aoki, the two witness some boys harassing girls from their school. Yui impulsively jumps to the girls' aid, violently attacking the boys. The police soon arrive and stop Yui before placing her under arrest. Wanting to take her in for questioning, Yui is startled by her own behavior and surrenders. Aoki, however, suddenly tries to free Yui from the officer's hold and he is arrested as well. Luckily, the two are let off with warnings. As it turns out, their actions were a product of Heartseed's latest phenomenon that forces their  impulses to go unrestrained.

Yui begins hoarding away in her room and when her friends visit her, she states she doesn't want to be near other people. Yui admits to being scared of herself, stating that her impulses were her own and deep down, a part of her really did want to hurt others. Inaba's impulse unleashes after she becomes impatient with Yui and angrily berates her for her cowardice. Yui is reduced to tears and Inaba apologizes but Yui states Inaba meant what she said. The StuCS would later become divided over how to deal with Yui's predicament, leading to a falling out between Taichi and Aoki and between Iori and Inaba.

After a week of hiding, Yui is once again confronted by Aoki and Taichi who are determined to help her. Aoki explains that while he loves Yui, he is also a huge pervert and how if he had his impulses unleashed, he would throw himself at Yui. Yui is disgusted, but Aoki then claims that he would never actually do that because he would be able to restrain himself through sheer force of will and states Yui can do the same. Yui is unconvinced so Aoki insists they go to a love hotel to put his theory to the test. Yui is further repulsed, but Taichi adds that now that Yui understands what it means to hurt someone, she will never let herself do it again. Yui begins to understand and agrees to return to school, but asks Aoki and Taichi to protect others from her if she loses control. At Aoki's suggestion, Yui rephrases her request to "please protect me." Aoki nobly gets down on one knee and accepts the responsibility as Yui smiles.

Later, Yui attends the class field trip but spends much of the time worrying about Inaba who is still bitter with Iori. Aoki, in his typical carefree fashion, insists she not worry. When the phenomenon ends, Yui returns home with the others, but worries Heartseed is far from through with them.

Kako Random arc
With her second term over, Yui looks forward to her winter break, but a new supernatural sentient similar to Heartseed, No.2, has other plans for her and the club. Initiating a phenomenon that  reverts the members to younger ages, Yui is forced to hide out in an abandoned building between 12pm and 5pm with the rest of the StuCS to prevent being seen by her family.

To make matters worse, Mihashi Chinatsu, Yui's old karate rival, returns and is furious to learn that Yui has quit karate and accuses her of breaking a promise that Yui does not seem to remember.

When Aoki is reverted to a child, he addresses Yui as "Nana's older sister". Yui later learns that she resembles Aoki's childhood love, Nana, which shocks and slightly upset her.

On their way to get more supplies, Yui is confronted by her sister,  Anzu and Mihashi who want to know why she quit karate. Yui is reluctant to share, which forces Mihashi over the edge and Yui's former rival challenges her to a match. Yui accepts, but she is quickly defeated and humiliated.

After another age reversion, Yui is freshly reminded of her past trauma and is left shell-shocked. Escorted by Taichi and Aoki home, Yui once again encounters a more civil Mihashi who wants to talk. However, Yui refuses to hear her out and angrily lashes out at Aoki when he tries to calm her, accusing him of only liking her because she resembles his ex-girlfriend. Aoki, having had enough of her attitude, tells her off, declaring that Yui needs to get her act together and she should stop running away from her problems. As she tries to defend herself, Aoki cuts her off saying she is once again making excuses and giving up and warns her not to criticize him. Hurt by Aoki's words, Yui is unable to defend herself, left shocked by what he said, while Aoki takes his leave after realizing his harsh tone.

Yui talks with Taichi at the park where she reveals that she remembers the promise she made with Mihashi, which was to fight her in the finals of the national karate tournament. Yui wonders how one would feel if they made a promise with a friend, but the friend never came through on the promise. Yui goes on, stating that she was once strong, but now she has to rely on others for strength and can't do anything in return. Afterwards, Yui takes her leave, while Tachi sadly does nothing but watch, realizing there's nothing he can do to help her. Later, Yui is given a heartfelt confession by Aoki who states that the one he loves is Yui and that her resemblance to Nana is irrelevant. Inspired and remembering what Aoki said about her making excuses and giving up, Yui decides it's her turn to take action and works to overcome her androphobia by embracing Aoki. Iori tells her she shouldn't push it, but Inaba warns her not to stop her. Her fear is intense but, refusing to run away, Yui only tightens her grip until finally, she stops trembling. Realizing how all she had to do was try, Yui declares she will not allow her androphobia to hinder her ever again.

Yui later helps Iori handle her family issues and after the phenomenon ends, she makes amends with Mihashi and announces she will return to karate. The two renew their rivalry and, calling her by her first name, Chinatsu, Yui exchanges phone numbers with her friend.

Michi Random arc
As the Student Cultural Society begin their final term as first years, Heartseed takes the opportunity to initiate his latest phenomenon which forces the club members to randomly communicate telepathically with each other. Confident that they will overcome this phenomenon like the others, the StuCS maintain high morale. However, trouble brews when Gotou reveals that he may leave his position as the Cultural Club's advisor due to conflicting commitments with the Jazz Band Club. Because Gotou will remain with which ever club performs better at the end of the year club presentations, Yui resolves to do her part to ensure Gotou stays with her club.

After a series of telepathic transmissions, Yui is startled to learn not only that Inaba is in love with Taichi, but that Taichi once again confessed to Iori but was turned down. After an enraged Inaba confronts Iori, Yui receives Iori's transmissions and sees a darker side of her friend that she never knew. Yui and the others then inadvertedly transmit their criticisms of Iori to her, alienating her from the group.

Amidst all the trouble, Yui still goes out of her way to present Aoki with chocolates for Valentine's Day, much the latter's joy. However, to Aoki's displeasure, she also gave chocolates to Taichi and many boys from her dojo. Growing increasingly distant from the others, Iori soon neglects to come to the clubroom altogether and a guilt-ridden Yui decides to take action. Meeting with Iori at a diner, Yui tries to coax her friend to return to the group but Iori remains cold, harshly criticizing that Yui doesn't understand what she's going through. Yui desperately says anything she can to comfort Iori but to no avail. Eventually, Yui cracks under the pressure and accidentally transmits her horror at what Iori has become. Cementing that they can no longer be friends, Iori walks away leaving Yui behind, defeated.

Later, a broken Yui calls Mihashi asking for advice, but her rival can only point out how Yui is relying on others once again. Suddenly, Yui is approached by Heartseed who asks what she thinks of the phenomenon. Heartseed cites how scared and vulnerable Yui is and, in her distress, she telepathically cries for help which is received by Taichi and Aoki. Realizing how she is once again relying on others to save her, Yui takes a fighting stance against the supernatural sentient, declaring she is done running away and will do everything she can take make it through the phenomenon with her friends. Heartseed mutters how boring Yui has become and takes his leave.

When Taichi arrives, Yui explains how she failed to help Iori. She then lectures a disheartened Taichi to man up and keep trying, believing Iori is waiting for him to save her.

When Inaba is kidnapped by some thugs who vandalized the Cultural Society's clubroom and destroyed their presentation, Yui, Aoki and Taichi set out to rescue her. Tracking Inaba down at an abandoned warehouse, Yui easily subdues most of the thugs but is left helpless when the last brute holds Inaba at knifepoint. With the help of Iori, Yui manages to knock out the final thug and the gang happily reunite.

Yui later apologizes to Iori for their previous encounter and the two girls revitalize their friendship. After Taichi is injured by a lone thug who managed to track them down, Yui stands guard outside Taichi's infirmary room, wary of any further surprise attacks.

With the phenomenon over, Yui helps rebuild and present her club's presentation. However, she is frustrated to learn that Gotou decided to remain advisor to both clubs, completely disregarding which presentation was better and making all of her hard work pointless. Yui would later assist Aoki in preparing for his make up exams. Taichi notes that every day they get a little closer, slowly but surely.

Yume Random arc
Despite having not practiced karate for several years due to her traumatic experience in junior high, Yui managed to retain most of her skill by the time she decides to start up again. This allows her to enter a karate tournament where she could potentially win a sports scholarship.