Naoya Mukai is having the time of his life after his childhood friend Saki Saki finally accepts one of his countless confessions. Ensuring that their relationship will stay strong, he spares no effort in showering affection to his now beloved girlfriend. However, one afternoon, another girl named Nagisa Minase suddenly confesses to Naoya following months of preparation. Even though he politely rejects her, Nagisa's irresistible charm and determination continue to attract Naoya. Wanting to fulfill both Saki and Nagisa's desires, Naoya ends up proposing a crazy idea—to date the two of them simultaneously, with both girls fully aware. This unprecedented state of affairs ultimately causes wacky and hilarious situations in whatever they do to keep their unusual relationship going.

Naoya Mukai has recently begun dating his childhood friend Saki Saki. Another girl, Nagisa Minase, confesses her love to him, but he turns her down. However, when she decides not to give up, Naoya finds her so cute he decides to convince Saki to accept Nagisa as his second girlfriend. Saki is so overwhelmed by Nagisa's cuteness she insists on becoming friends straight away. Naoya manages to explain his desire to date them both, and though Saki punishes him, she is eventually convinced by Naoya's honesty and Nagisa's cuteness and gives permission. Naoya suggests they move in together as he lives alone. On the first night, Saki is impressed by Nagisa's housewife skills, but is slightly jealous of her larger breasts. Nagisa offers to let Saki sleep with Naoya first, but Saki admits their relationship is not sexual yet. This leads to an awkward conversation where Naoya admits he would like a threesome. Saki admits she is tempted because of Nagisa's cuteness, but still insists Naoya is a pervert for suggesting it. Naoya decides to delay having sex until they are all more comfortable with each other, but is surprised when Saki seems disappointed, though she violently denies it.

Even If That Isn't the Right Way

For their first night, Naoya suggests everyone sleep in the same room. Nagisa moves into Naoya's futon to talk, causing Saki to think they are having sex. As such, both girls move into Naoya's futon to be close to him. Later that night, Nagisa decides to spy on Saki's phone to learn more about her, only to find it contains multiple searches about sex. Saki almost catches her, but Naoya takes the blame and is punished. Nagisa reveals while preparing her confession she forgot to attend school. Naoya insists they spend all day studying, though it soon becomes clear Nagisa struggles at math. Despite claiming she has to use the bathroom as an excuse to cheat, she gets the answers wrong anyway. At school, Saki insists no one can know about their relationship, but when Naoyo sees Nagisa has no friends, he attempts to reveal everything, only for Saki to stop him. Saki reveals she is worried people will think Naoya no longer cares about her. However, when Nagisa agrees they should only interact at home, Saki is touched by the offer and instead decides they can interact in secret where others cannot see them.

How Nagisa Feels

The three decide to eat lunch together in the gym storeroom, which has a padlocked door to ensure privacy but an open window they use as an entrance. Saki realizes with Nagisa and Naoya doing cooking and household chores and Naoya doing his best to make both girls equally happy, she is not actually bringing anything to the relationship and fears Naoya will soon prefer Nagisa over her. She becomes determined to do something for Naoya, but with sex not an option, she tries cooking but burns the curry. Desperate to impress Naoya, Saki creeps into his room to try and have sex, but he turns her down. She then becomes upset, believing he prefers Nagisa's larger breasts and returns to her parents' house, which is only next door. Nagisa feels guilty enjoying being alone with Naoya. Naoya tries various ways to apologize and exhausts himself over three sleepless days, but Saki rejects him every time. Still feeling guilty, Nagisa decides to help and tricks Naoya into groping her breast where Saki can see, which causes Saki to rush back in a jealous rage, where Nagisa insists she talk to Naoya.

A Place for Three

Saki admits she feels inferior to Nagisa and it annoys her that Naoya does everything without asking for anything in return. Surprisingly, Nagisa agrees that Naoya does too much for them. Naoya realizes by taking all the responsibility, he was actually being selfish. With Saki back home, Naoya passes out from his three days accumulated exhaustion. Saki and Nagisa debate how exactly they will become equals and realize they both like gaming. Nagisa is terrible at gaming and Saki feels better knowing there is something she is better at and they become friends. While watching another player called Milika streaming her games online, Naoya sees a school uniform in her thumbnail and realizes Milika attends their school. During lunch in the gym storage, Saki forgets to lock the window and another girl, Rika Hoshizaki, climbs in. Naoya panics and accidentally admits everything, amusing Rika who teases them about revealing their secret, until Nagisa recognizes her as Milika, causing Rika to also panic. As everyone now has secrets they do not want revealed, they all agree to keep quiet. Realizing they are actually decent people despite their unusual relationship, Rika decides she wants to join them as Naoya's third girlfriend.

Girlfriend and Girlfriend

Saki and Nagisa deduce Rika only wants a boyfriend in case her fans begin stalking her. Naoya refuses to date her as her motivations are shallow and selfish. Having never been rejected before, Rika attempts to entice him. An accidental comment by Saki reveals they are living together so Rika offers to pay the rent and bills. However, when Naoya still rejects her, she flees. The next day, Rika follows them home and begins living in a tent in the backyard, shooting risqué exercise videos in her Milika persona to keep warm overnight and earn money to buy items needed to live outdoors. The next day, Rika realizes exercising has made her stink and is forced to improvise a shower wearing a bikini. The girls realize Rika might actually be stubborn enough to live in their backyard indefinitely. To keep Naoya's mind away from Rika, they attempt to seduce him in the bath wearing bikinis, but their nervousness and Naoya worrying about the Rika situation means it does not go to plan. In the end, Naoya makes them feel better by promising to spend more time with them and less time worrying about Rika.

A Third One!?

Naoya is determined to get rid of Rika as he is worried he might be too weak-willed to resist her forever. The girls decide to help get rid of her by donating her belongings to charity. Rika tries to stop them by convincing passersby Naoya is a groper, but he refuses to let her go despite everyone staring and even offers to replace everything if she leaves. Rika cannot understand why an admitted two-timer refuses to date her and he explains it is because he is committed to making Saki and Nagisa happy. This makes Rika develop a real crush on him. Rika's father appears and learns everything Rika has been doing, including her risqué Milika videos, so he takes her phone to permanently shut down her account. However, Naoya stops him as he knows Rika is an artist and how much work she has put into developing her Milika persona. Naoya defending her turns Rika's crush into actual love. She agrees to go home to think, but only if her dad allows her to keep her Milika account. Saki and Nagisa become depressed over how much more trouble Rika might cause now she actually loves Naoya.

Tsun Is Dere

Saki's mother, who does not know about Nagisa, is concerned Saki and Naoya are not having sex. Saki realizes due to Naoya's easily flustered personality and determination to treat his girlfriends fairly, he might never have sex with either of them. She attempts to seduce him as a bunny girl, but he insists on their no sex rule and when he does touch her breasts, Saki panics and punches him, but is happy she aroused him. Nagisa becomes suspicious when she finds the bunny costume in the laundry and confronts Naoya. Naoya insists nothing happened so Nagisa comes to believe he has a costume fetish and dresses as a sexy maid. Naoya is aroused but still sticks to the rule. That night, Nagisa accidentally calls Naoya "Master" in front of Saki, who luckily decides she misheard it. At school, Rika tries to talk to Naoya. Erroneously believing she is angry he rejected her, he offers to let her humiliate him online. Naoya's clumsy attempt to apologize only make her want to confess her love, so she instead thanks him for saving her Milika account. She later admits to herself she loves Naoya, which is overheard by Saki.

The Girlfriends' Challenge

Rika talks to Naoya casually in class so Saki jealously insists he stay by her side, though Naoya mistakenly believes Saki is just lonely. While escaping Rika, they are forced to change for PE in the same room. Nagisa lures Rika to the roof with the photo she kept proving Milika is a student at the school, allowing Saki and Naoya to escape. Later, Nagisa admits to being jealous Saki and Naoya got to be close all day. Saki offers to leave them alone so they can cuddle, but Naoya insists she stays to watch. Saki is surprised watching makes her excited and wonders if she might have an NTR fetish, so she punishes Naoya. Rika continues to talk with Naoya, who starts to suspect Rika might have a crush on him. The girls, happy Naoya is so dense, convince him Rika is probably in heat and after any available man. Naoya is mistakenly convinced this happens to all women and offers himself to Saki and Nagisa should they encounter the same problem. Naoya apologizes to Rika for thinking she had a crush on him, embarrassing her in class, so she drags him away for a private talk.

Obviously in Love

Naoya explains why he thought Rika liked him when really she was just in heat, causing her to become furious at the obvious lie and at Naoya for believing it. In the end, she claims to just have a cold. Naoya explains that if she did like him, he would still turn her down so as not to upset Saki or Nagisa. Rika stubbornly tells Naoya she likes him in front of the whole class then drags him to the gym storeroom where she reveals her plan, to keep flirting with him until he falls in love with her. However, when he keeps on refusing, she snaps and kisses him before running away. Another girl from the class overhears this from outside the storeroom. Saki and Nagisa are depressed Rika kissed Naoya first, but Saki decides it was not a real kiss since it was a surprise with no emotion, so when she kisses Naoya it will be the real first kiss. Naoya is confused about everything so he apologizes and suggests a fresh start by going on a date, something they have all been too busy to do yet, so Saki demands a hot spring date.

The Tsun's Dere Gets Outed

The other girl, Shino Kiryū, tries to talk to Naoya but Saki prevents it. While Naoya, Saki, and Nagisa are out shopping for the hot spring date, they are followed by Rika. Nagisa wonders if she should try to kiss Naoya, but when she sees how much Rika kissing Naoya has stressed Saki out, she decides to support her instead. Rika soon learns about the date. Shino is determined to find out if Naoya is two-timing Saki. The trio head to Hakone where Naoya decides they will do everything they cannot do in their hometown, so he holds both Saki and Nagisa's hands at the same time. Saki suspects they might have sex during the trip. They find Rika is already at their hotel, as is Shino who confirms Naoya is two-timing Saki with Nagisa. However, Nagisa blackmails Rika with her Milika photo into pretending she came with her and not with Naoya. When Naoya learns about Nagisa's self-sacrificing plan, he is unwilling to leave her out of the date, sneaks onto the roof and asks that she join him and Saki, but she refuses. Now inadvertently alone with Rika, she decides to seduce him.

Can't Wait for the Hot Springs

Rika is shocked their kiss did not make Naoya obsessed with her and decides to just have a normal conversation. Their talk abruptly ends when Rika's towel accidentally falls off. As Naoya flees, he falls into the women's hot spring where Shino is bathing. After getting over her embarrassment, she demands to know if he is cheating on her friend Saki. Naoya tries to flee so she grabs him, causing him to fall and her towel to come loose. Saki and Nagisa enter the hot spring at that moment and see Shino on top of Naoya. While Saki is frustrated, Nagisa realizes what probably happened and takes a photo to blackmail Shino. Shino flees and Saki punishes Naoya. Nagisa tries to leave them alone, having promised to support Saki, but Naoya refuses to leave her out. They are caught by other hotel guests so Naoya is punished again. Saki tells Nagisa she does not have to put herself aside so much and Nagisa explains she is used to having to work extra hard just to be average, which is why she is happy Naoya accepted her and is happy with their current relationship.

Hot Spring Tropes

Nagisa explains the first time she saw Naoya, she instantly fell in love with him and devoted herself to becoming his ideal woman. Naoya overhears this and tells her to stop holding back. Embarrassed he heard everything, Nagisa flees. Shino bumps into Rika and when Nagisa, Naoya and Saki run past, they join the chase. Nagisa insists she has to stay subordinate to Saki or their whole relationship will fail. Saki, Rika, and Shino fall back from exhaustion so Nagisa and Naoya continue without them. Naoya eventually catches her and insists that whatever problems occur, he will fix it. The others catch up and Nagisa admits to Shino she is also dating Naoya. Saki accepts this and happily declares they are now rivals for the position of senior girlfriend before they flee from Shino and Rika and finally begin enjoying their vacation. Later, Shino criticizes Naoya for two-timing and Saki for accepting it, but is shocked when Naoya reveals he plans to tell Saki's mother, though Saki furiously forbids this. Shino decides to somehow split them up for Saki's sake and thus is furious to learn that Rika also loves Naoya and accuses him of being a three-timer.

Girlfriend, Girlfriend

Kanojo mo Kanojo

Naoya Mukai's crazy lifestyle of balancing his time between both of his girlfriends, Saki Saki and Nagisa Minase, is still as hectic as ever. Additionally, the blonde bombshell Rika Hoshizaki also has her sights on Naoya, complicating his already convoluted love life. As if things could not get more ridiculous, another girl inserts herself into the situation: Shino Kiryuu, who is determined to end Naoya's two-timing and ensure Saki's happiness. However, Shino harbors secret feelings for Naoya—a longing she believes she must forsake—yet simply cannot due to the deep attraction he inspires.