Yami/Plot

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" had begun. I t's stated  the cause of it is because Yami had a "peace of mind", something a weapon should not have and the heartfelt acceptance 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.