Naoya Mukai is in a relationship with Saki Saki, but another girl, Nagisa Mizuse, asks him out. He makes the unthinkable decision of asking them if they would be up for both dating him at the same time.

Naoya, Saki and Nagisa are now living together. Keen to learn more about Saki and Naoya, Nagisa gets into her phone and looks through her browser history.

Naoya, Saki and Nagisa search all around school for a place where they can eat lunch in peace, without anyone finding out that they are in a relationship.

Saki returns to Naoya’s place and plays some games with Nagisa, who is utterly horrible at it. They notice that a gaming MeTuber seems to have the same uniform that they do.

Rika, who’s outed as a popular MeTuber, insists on dating Naoya. When he rejects her, she decides to try to live at his home along with the other two.

Rika starts her not-so-laid-back solo camping life in Naoya’s yard. Naoya and his girlfriends decide that enough is enough, and try to have her camping gear taken away.

Saki realizes Rika is serious about Naoya, and begins frantically looking for ways to keep her from joining their relationship.

Rika comes to hang out in Naoya and Saki’s classroom, causing sparks to fly between her and Saki.

Saki tells Naoya that Rika’s apparent crush on him is only the result of her being in heat. She insists that this is a real thing, and Naoya buys it.

As a way to clear the air after Rika kisses Naoya, he, Saki and Nagisa decide to go on vacation at a hot spring.

Nagisa spends her time on vacation with Rika to try to keep Shino from finding out that dating both her and Saki.

Nagisa had insisted on supporting Saki on the hot spring vacation, but when Saki confronts her about it, she begins to speak her mind.

The trio want to enjoy their summer break, but first they have to pass their exams, and it turns out poor Nagisa is an extremely poor student. Saki wonders if Shino could be convinced to help her study, even though she disapproves of their relationship.

Shino moves in with the trio, intended to begin work on breaking them up. Saki tells everyone stories about how they met in middle school., which involved Saki making Shino play video games. It turns out Naoya also has a story about how he met Shino...

The gang is heading out to the fireworks festival. After a failed experiment (which was not Nagisa's fault), Shino decides that Saki and Naoya need to have their first kiss with the fireworks display helping to set the mood.

Everyone's at the fireworks festival, but Naoya and Saki have been separated, foiling Shino's plans. Instead, Naoya has ended up watching the fireworks with Nagisa despite their plans to the contrary.

Shino is frustrated and furious about Naoya and Saki's failure to kiss at the fireworks festival. Saki wins a bunch of camping gear and a campsite coupon, so everyone decides to go enjoy a camping trip.

Rika kidnaps Naoya after drugging the others, hoping to seduce Naoya while the others are away. Naoya firmly rejects her advances, but this only inspires Rika to keep trying harder. Naoya then realizes escape is the only way out.

Rika moves in with Naoya and the others, and insists that sleeping in the same room with him in a non-sexual fashion should be completely permissible. Naoya agrees, but only if all the girls get to take turns sleeping in his room in a non-sexual fashion.

Saki really wants to go to the beach, but conversation about the trip is interrupted by Mirika drying her bra out where Naoya can see it. One thing leads to another, and the girls are soon competing to see whose bra excites Naoya the most.

Naoya and the girls depart for Okinawa. The trip gets off to a bumpy starts when their plane encounters turbulence, and Naoya panics. Once they get to their vacation home in Okinawa, the girls put on their swimsuits.

Mirika has kidnapped Naoya and locked him in a room while Saki and the others try to find the key. Shino is taken aback by Mirika's resolve, and begins to question the way she's been hiding her own feelings.

Shino and Naoya are stranded on an uninhabited island, and Shino has ended up naked again. Has the time finally come for Shino to confess her feelings? Meanwhile, Saki and the others have realized that Naoya and Shino are missing.