To Love-Ru Edit
In the beginning, he lives alone with his sister due to their parents always away to work. Rito is quite shy when it comes to girls. He has a crush on a girl named Haruna Sairenji, whom he constantly tries to confess to but always backfires on him (a running gag in the series). One day, after another failed attempt to do so, he encounters an (naked) alien princess named Lala while in his bathtub, who is on the run from home because of her father forcing her into arranged marriage. It's stated in the anime that due to accidentally groping her breasts he is now engaged to her. At first, she only pretends to show affectionate feelings for Rito at the beginning of the story so that she can stay on Earth, but came to truly love him and desire to marry him for real and came to live at his home.
Since Lala's arrival, Rito goes through a lot of trouble that comes from space, such as her other fiancé candidates and many others. Although thanks to Lala, he has also befriended many characters, including Haruna, who, unaware to him, also has feelings for him.
In addition to the girls he already has to choose from, Rito's love life would soon become even more complicated with the arrival of more girls, some of whom either love him, hate him, or actually both. Yui Kotegawa is a tsundere who becomes a very reluctant additional love interest after slowly warming up to Rito. Oshizu Murasame is a ghost girl brought back to life via an artificial body constructed by school doctor Ryoko Mikado. Run Elise Jewelria is another alien girl who is Lala's rival for Rito's love but occasionally transforms into her male body and personality, Ren, who is also Rito's rival for Lala's love. And Golden Darkness is an alien living weapon and assassin hired by one of Lala's suitors to kill Rito, but after her job is annulled, she stays on Earth under the pretense of killing him later.
Soon, Lala's younger twin sisters, Nana and Momo, arrive to live with Lala in Rito's house. Nana is a tomboyish tsundere and has taken to calling Rito a "beast" for his ever growing company of girls and his perverted antics. But the sweeter and more mischievous Momo quickly grew smitten and affectionate with Rito's innocent nature and greatly enjoys his accidental perverted tendencies.
Despite his enduring feelings for Haruna, Rito shows signs of developing deeper affection towards Lala. As the story progresses, he starts to show affections for Lala, but is unsure if what he feels is actually love. This is shown again when he couldn't help but think about Lala, even though he was naked with Haruna. By the end of To Love-Ru, as pointed out by Saruyama, Rito has changed a lot around women since Lala came into his life. It was at this point that he realized he is in love with Lala, but he is also in love with Haruna.
In the end of the original series, he confesses to Lala, but tells her he also loves Haruna, yet she is happy on both parts (knowing that Haruna also loves him). He is confused as polygamy is illegal in Japan, but Lala replied that onced he and her are married, he will be the next king of Deviluke, meaning the laws of Earth would no longer apply, making polygamy legal for him. Lala then forces him to go tell Haruna (strapping a jet pack to his back). Right before Rito was about to tell her, she moves out of the way (due to her swimsuit being undone by Oshizu's ability) and just like whenever he confesses to her, it backfires on him, leading him to state "I love you" to Yui, Run, Nana and Mikado.
To Love-Ru Darkness Edit
In To Love-Ru Darkness, although Rito is happy he told Lala about his feelings, he is depressed about his recent failure in confessing to Haruna, instead accidentally doing so to four other girls, whom he tried to convince that he said "I love the pool", although he's not sure if they believed it. Rito might be reconsidering about Lala's idea of being with both her and Haruna, thinking it be treating her as insurance, but shrugs it off. However, Momo, who has already fallen in love with him, approaches him saying otherwise and that there are lots of girls who are secretly in love with him and initiates to build a harem for Rito, which she continually organizes in secret with the hope that she may also be included into Rito's love life someday.
Currently, Rito has not yet confess his love to Haruna, but instead decides to take his time to sort out the feelings he has for both Haruna and Lala.
Meanwhile, Yami has yet to kill Rito, but instead spends her time living a peaceful life on Earth and forming a close friendship with Rito's mature younger sister, Mikan, and an abusive love-hate relationship with Rito. Yami gradually learns to re-adapt herself with the peaceful life she hasn't enjoyed in a very long time, until she meets Mea Kurosaki, another transformation weapon of the same program that created Yami, hence, her little sister. Mea wishes for Yami to finish her mission to kill Rito and return to space with her, but Yami and Rito urge her to adopt a life of peace on Earth and embrace friendship.
In the meantime, Run spends most of her time working as a popular idol, but eventually makes the time to spend a day with Rito. At the end of their date, Run expresses her grief that because she shares a body with her male counterpart, she will never be a complete girl and can never truly be with Rito. But surprisingly, immediately afterwards, Run's body reaches the point of adulthood, where her body and Ren's separate from each other, now with each gender in his and her own body. The two former counterparts are overjoyed with the separation, and Run rejoices that she now truly has as much a chance for Rito's love as a real girl.
As Mea contemplates heeding Rito's and Yami's urges to embrace her emotions and friendships and rejecting her master's teachings that she is a heartless weapon, her friendship with Nana become strained when she appears to callously pass off their friendship as fake. Rito comforts Nana when she is heartbroken and gave her the courage to reconcile with Mea. After Mea re-embraces Nana as a true friend, both Mea and Nana open up more to Rito, though Nana is unlikely going to stop calling him a beast anytime soon.
Rito's relationship with Yami remains highly confrontational, especially as Rito's clumsiness and perverted antics become more frequent and more violating than ever before, which Yami responds with violent fury. However, Rito's kindness does slowly warm up to Yami, and she gradually sees in him and his sister the peaceful family life that she once had and still desires deep down. Yami eventually confides in Rito about her childhood. She explains to him that she is a living weapon created by Dr. Tearju Lunatique, a kindly scientist who named her Eve and raised her like a younger sister, until the organization where they lived chased Tearju away and raised Eve to be a heartless weapon. Rito is appalled with Yami's unfair life at the hands of the organization and expressed his sympathy for Yami, further developing her feelings for him.
When Tearju arrives to their school and becomes Rito's substitute homeroom teacher, Rito rejoices to Yami's chance to reunite with Tearju and enthusiastically encourages Yami. Unfortunately both Yami and Tearju are still too reluctant and shy to see each other after such a long time. Mea is also hesitant and reluctant to accept Tearju, since she is a hindrance to Mea's hope that Yami returns to being an assassin. Rito continues to encourage them both to accept the value of family and expresses his hope that Yami would be happy. After grudgingly listening to Rito, Mea reluctantly encourages Yami as well.
After Mea begins to open up to her friends, Mea's master, Nemesis, decides that she would also like to meet with the others, starting with Rito, Momo, and Yami, but her introduction was less than a comforting one due to her suspicious and eerie personality as well as her mischievous and erotic tendencies. She reveals to them that her goal is to make Yami activate her Darkness ability, a forbidden transformation. Believing that Darkness will activate inevitably, Nemesis decides to bide her time and acquaint herself with the others, and has been making random appearances since, mostly to Rito, whom she claims as her servant and uses as her endless source for erotic entertainment.
Lala suddenly decides to re-approach Rito romantically instead of waiting for him to finally confess to Haruna. She tries asking him for a kiss, but Rito remains too indecisive between Lala and Haruna, and needs more time to certify his own feelings. Lala happily agrees, and settles for kissing him on the cheek and continues to wait.
Overtime, just as Yami and Mea learned to accept the life of peace that they found on Earth, Yami's Darkness transformation activates against her will, which transforms Yami into a psychotic and much more erotic version of herself, with a new outfit to match her perverted new self. She immediately uses her new powers to teleport Rito to her side and causes all sorts of perverted mayhem to all girls nearby. She explains that she's in love with him, and as he is her target, she wishes to give him a very ecchi way to die by her hands. Lala manages to protect Rito from Yami as long as she could, but was barely a match against Yami's potentially apocalyptic power.
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. In order to save the world, Rito must molest Yami! However, Rito must do shameless things to her at his own will, which may prove to be a challenge for Rito, who is impossibly clumsy and innocent to a fault despite his near superhuman perverted powers. Even Yami firmly believes that Rito is far too innocent and clumsy to molest her successfully, and Yami is currently unharmable by his usual perverted falls. Rito (and Nana) reluctantly agree with the plan if it could bring Yami back to normal before she destroys the Earth.
Mea, Nana and Momo together fight Yami to give Rito an opening. As Rito charges at Yami, he easily trips again over a very small bump, which could spell complete failure for the plan. However, Rito successfully manages to break his fall and land on his feet, much to the shock of his allies. Using the Principal's example as a model, Rito strips to his boxers and tackles Yami. Desperately suppressing his own wimpy true self, Rito relentlessly attacks Yami with his perverted talents at full power, surprising and overwhelming the superweapon girl. After a while of relentless groping, eventually Yami slaps Rito and reminds him that she hates ecchi, signifying that she has returned to normal and Rito's shamelessness has saved the world, just in time for Mikan to catch them together dressed in nothing but boxers on Rito and a perverted-looking outfit on Yami.
After peace returns and everything is back to normal, Rito is worried that Yami is angry at him for groping her earlier. Yami soon approaches him with the hopes of thanking him for returning her to normal, but before she could, Rito quickly apologizes and stupidly exclaims all of the perverted things he did to her while they were in public with people around. Yami angrily attempts to shut him up, and when he trips over her again, with the usual perverted results, the conversation ends on a bad note.
Afterwards, Lala's mother, Sephie Michaela Deviluke, arrives to check up on Lala. She has a happy conversation with her daughters at Rito's house. Rito learns that Sephie must always wear a veil over her face because as a Charmian, her beauty has enough seductive power to drive all males crazy and make them lust for her. But as she is about to join her daughters in a hot spring in Nana's cyber safari park, Rito unintentionally walks in on her, and as expected of his clumsiness, catches her both nude and with her face exposed. At first, she was terrified that her beautiful face would turn Rito into a perverted beast like all other men before, but Rito has shown that he is surprisingly immune to her seductive beauty. She realizes that Rito has a strong conviction that could resist her beauty and compared him to her husband. She takes a liking to him and jokingly offers all three of her daughters to him, and when he flusters at her joke and offhandedly mentions a harem, Sephie knew almost immediately that Momo is plotting a harem plan. Despite Rito's usual perverted antics, Sephie had a happy time during her stay and leaves satisfied.
Rito and Lala come visit Haruna at her sister's apartment. Lala hopes that Haruna advances her relationship with Rito, suggesting with a sudden kiss. But after an accident with Lala's invention, Rito and Haruna are both shrunken to a tiny size. When Haruna's lovey-dovey parents arrive to visit, Lala uses Peke to disguise herself as Haruna while Rito and Haruna hide until their shrink wears off. In order to protect themselves from Haruna's perverted pet dog, Maron, Rito and Haruna seek refuge by hiding in Haruna's panties. And as they struggle to hide, Haruna accidentally kisses Rito on his lips.
The next day, neither Rito nor Haruna know what to make of their accidental kiss. Rito is worried that Haruna would be angry at him. But after both are pressured by Oshizu and Momo to finally confess to each other, Haruna, at the very last second, instead apologizes to him for the accidental kiss, which he forgives. Despite the kiss, their relationship has pretty much gone nowhere.
Soon, Nemesis reappears in front of Rito while being pursued by the Devilukean royal guard, led by Zastin, who has been investigating her since the Darkness incident. Zastin arrives and reveals to Rito that Nemesis' plan is to destroy the political system established by Planet Deviluke and plunge the universe into another war. But instead of fighting Nemesis himself, Zastin uses a device to teleport Nemesis, Rito, and himself, to a location in cyber space, where they are confronted by none other than Gid Lucione Deviluke, the king of Deviluke.
Gid fights Nemesis to stop her crimes against Deviluke and easily overwhelmed her in battle. When Gid brutally defeats Nemesis to the point her body would disappear into nothing, Rito, out of compassion, offered to let her live inside his body until she can recover. Believing that he has no obligation to help her, Nemesis finds Rito willingness to save her and trust her with his own body very strange, but nevertheless accepts his offer and fuses into his body. Rito bravely convinced Gid that he can change her and even offering to die with her if she doesn't change, expressing his willingness to go that far to save her as his responsibility as a man. Gid relents, now intrigued to see how Rito proves himself a true man. Nemesis is now recovering inside Rito, where she is able to control his movements for brief moments, which she quickly uses for perverted mischief, and will likely continue to in the days to come.