When she makes her appearance in To Love-Ru, she was hired by Lacospo, one of Lala's arranged suitors, to kill Rito Yuuki, who has unwillingly become Lala's marriage candidate. But when Lacospo effectively annuls the job, she decides to take her time and, under the pretense of still needing to complete her mission to kill Rito, stays on Earth. As she spends more time on Earth, she builds a very strong relationship with Rito's mature younger sister, Mikan Yuuki and with Rito himself.

While Yami rediscovers her own humanity and interacts with more people she can call her friends, she becomes uncertain if she truly belongs in such a peaceful life she has found during her stay on Earth, or her real place is inevitably her old life as a cold assassin. As she continues to spend more time on Earth, she becomes more used to living in a more peaceful life and becomes more comfortable around other people, mostly around Mikan, her only genuine friend. Yami has grown to care greatly for Mikan that she would protect and save her from her enemy Tyrant Azenda, even going to the point to sacrifice her own life just to save her.

Yami's other most significant relationship is with Rito, with whom she develops a trusting but often humorously abusive relationship. Yami frequently puts up with Rito's perverted antics, and very frequently beats him up for them. Overtime, she develops mixed and undefined feelings for Rito, but trusts him with things she hasn't confided in anyone else. She tells Rito about her past with her creator, Tearju, who named her Eve, and how the evil organization tried to take advantage of her until it collapsed, at the time when King Gid Lucione Deviluke triumphed in the Galaxy's Unification Wars.

During her stay on Earth, Yami spends much of her time at taiyaki vendors, since taiyaki is all she ever really eats. She also spends much of her time at libraries and around Sainan High School, where she is often seen borrowing and reading books. Since the students are already aware that Lala and her sisters are aliens attending their school, it came as little surprise to the other students that Yami is also an alien.

In To Love-Ru Darkness, Yami decides to enroll in Sainan High, where Rito, Lala, and most of the main characters attend. There, she meets Momo, the little sister of Lala. Momo intends to protect Rito from any threat, but hopes for Yami to join their side. Unknown to Yami, Momo intends to add her into her Harem Plan, her plan to have multiple girls fall in love with Rito and someday all marry him.

At school, she also meets Mea Kurosaki, another transformation weapon of the same program that created Yami, hence, her little sister. She has been sent to Earth by her master Nemesis to take Yami away and revive the old heartless/murdering self that she once was. However, despite her cheerful facade, Mea is also confused and conflicted deep down, perhaps more so than Yami. Yami does not show much attachment to her newly discovered little sister, but she encourages Mea to learn to live surrounded by others and open up to friends.

Eventually, Tearju learns of Eve's presence on Earth, and soon arrives to become a teacher at Sainan High, in the hopes of finally reuniting with her. Although aware of each other being nearby, they remain reluctant to face each other directly. Yami forgives Tearju for escaping the organization without her, and says that she is relieved that Tearju is alive and well. But their reunion and relationship still remain hesitant and awkward at best. Yami did not return to school again until Tearju becomes her homeroom teacher, and after much convincing from Rito.

Recently, in Darkness Chapter 37, Mea was forced to use her transformation powers in front of many others to save the school from a micro black hole. Yami then appeared and introduced Mea as her little sister. Mea was then warmly welcomed by all of the students present.

In Darkness Chapter 39, just when Yami felt accepted by everyone and no longer sees herself as a weapon, the activation of the "Darkness Transformation" begins. It's stated the cause of it is because Yami had a "peace of mind", something a weapon should not have and the heartfelt acceptance of it. When the transformation is complete, not only has her appearance changed (much more erotic clothing, and the horns on her head), but her personality changes as well to a more psychotic and perverted attitude. Yami brings Rito over through a wormhole she created and desires to have him do more ecchi things to her. She then expresses her love for Rito, her target, by molesting all of the girls around him, with the intention of giving him a fitting and ecchi place to die. 

Lala arrives to defend Rito. A fight ensues between Yami and Lala, and after a series of exchanges between Yami's perverted tactics and Lala's inventions, Yami attacks Lala with enough force to destroy the whole planet, which Lala's tail laser barely managed to deflect. After using her tail laser at full power, Lala is reduced to a body of a child. Mea, Nana and Momo arrive to stop Yami. Mea deduces that Yami's obsession with Rito and newly perverted tendencies are caused by a bug inside her as a result of Rito's influence on her and her feelings for Rito. She comes up with a plan to have Rito stimulate the bug inside Yami to make her return to normal by doing one of the few things he's good at: molesting her! Though Yami is confident that the innocent Rito wouldn't have the nerves to do shameless things to her of his own will. After Mea, Nana and Momo join together to create an opening, Rito desperately suppresses his usual character and begins his shameless assault on Yami, groping and molesting her relentlessly until she is overwhelmed with stimulation, much to her surprise. After a while of relentless groping, eventually Yami slaps Rito and reminds him that she hates ecchi, signifying that she has returned to normal, just in time for Mikan to arrive and find her in a perverted-looking outfit. 

After peace returns to their lives, Yami goes around the school to apologize to all of the students whom she troubled during her Darkness transformation, including Lala, whom she gives a box full of milk bottles to help her grow back to her normal body size. She is also reluctant to thank Rito, whom she owes for returning her back to normal. She attempts to thank him, but his usual blunders and clumsiness angers her again, and she angrily reminds him that he is still her target and that she has no feelings for him, despite what she said during her Darkness transformation. 

Ever since she has returned to normal from her Darkness transformation, Yami's personality displays significant changes. While she is still mostly her usual self, she now has stronger tsundere tendencies, mostly regarding Rito. She tries to be more respectful to Rito, but only to end up shouting in angry outbursts instead. Mea encourages her to become more friendly with him, and after getting unwanted advice about love from Mikado, Yami reluctantly approaches Rito again. As expected, her attempts to become friendlier with him are awkward at best, and ends with yet another perverted accident. Yami angrily storms off, but will likely try to becomes friends with him again.   

Yami eventually admits to Mikan she is in love with Rito. Both Mikan and Mea now support her crush on him, with the latter telling her to stop informing him he is her target and instead admit to him she loves him. She is later informed by Mikan that Kuro is targeting Rito; she later meets up with Kuro, Rito, Mea and Nemesis and activates her Darkness transformation, this time out of her own will and more quickly than previously.

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