16-year-old super-studier Nagi Umino, second-year student at the Megurogawa Academy high school, was switched at birth. On his way to a dinner to meet his birth parents, he accidentally meets the brash, outspoken, Erika Amano, who is determined to make Nagi her fake boyfriend as she never wants to actually marry. But once Nagi makes it to dinner, he finds his parents have decided to resolve the hospital switch by conveniently having him marry the daughter his birth parents raised...who turns out to be none other than Erika herself! The Megurogawa Academy culture festival has begun! Amidst their nervousness for the M-1 competition, Nagi and Erika walk around the school together. If they lose, their cohabitation will end... What's the “bomb” they've prepared to ensure their victory?! What is Soichiro planning?! And what's the answer that Nagi has reached?!

16-year-old super-studier Nagi Umino, second-year student at the Meguro River Academy high school, was switched at birth. On his way to a dinner to meet his birth parents, he accidentally meets the brash, outspoken, Erika Amano, who is determined to make Nagi her fake boyfriend as she never wants to actually marry. But once Nagi makes it to dinner, he finds his parents have decided to resolve the hospital switch by conveniently having him marry the daughter his birth parents raised...who turns out to be none other than Erika herself! Nagi is feeling anguished after learning about Erika's older brother, so he goes to Erika's hotel mogul father to find out the truth. But his plan ends up backfiring as the situation grows even more complicated...though it's nothing a bike date with Hiro and a beach trip with all three girls can't fix! Time for Nagi's ultimate summer to begin!

16-year-old super-studier Nagi Umino, second-year student at the Megurogawa Academy high school, was switched at birth. On his way to a dinner to meet his birth parents, he accidentally meets the brash, outspoken, Erika Amano, who is determined to make Nagi her fake boyfriend as she never wants to actually marry. But once Nagi makes it to dinner, he finds his parents have decided to resolve the hospital switch by conveniently having him marry the daughter his birth parents raised...who turns out to be none other than Erika herself!

After being swapped at birth, Nagi Umino is currently a second-year student at a prestigious high school. One day, he runs into Erika Amano, a spoiled rich high school girl who says she's on the way to meet the fiancé her parents arranged for her, and ends up pretending to be her boyfriend. But the two of them soon learn that they'd been swapped with each other as babies, and their parents decided to engage them to each other... Nagi and Erika have a new addition to their household: their younger sister Sachi! Nagi and Sachi have a big fight when he tries to send her back to their parents, but Sachi is actually just unable to say how she wants to spend more time with her big brother. Throw in an amusement park date with Nagi's beloved Hiro and some rapid bonding with Erika and this four-way love knot quickly grows more and more complicated!

Nagi and Hiro have broken up! After a shocking Christmas, Nagi works to regain his happiness, and Hiro tells her true feelings to Erika. As the new year rolls around, Nagi finds himself busy with cleaning the Ama-Umi House, the Amano Group year-end party, and Ai-chan's new year's concert. Amidst all that, Sachi's high school entrance exams are closing in…and then she confesses her feelings on New Year's evening?!

After being swapped at birth, Nagi Umino is currently a second-year student at a prestigious high school. One day, he runs into Erika Amano, a spoiled rich high school girl who says she's on the way to meet the fiancé her parents arranged for her, and ends up pretending to be her boyfriend. But the two of them soon learn that they'd been swapped with each other as babies, and their parents decided to engage them to each other... Spoiled rich girl Erika Amano and son of restaurant owners Nagi Umino were swapped with each other at birth, and their parents have decided that the two of them should get married. On top of that, they've forced the couple to start living together! How will they cope with these cruel twists of fate?!

16-year-old super-studier Nagi Umino, second-year student at the Meguro River Academy high school, was switched at birth. On his way to a dinner to meet his birth parents, he accidentally meets the brash, outspoken, Erika Amano, who is determined to make Nagi her fake boyfriend as she never wants to actually marry. But once Nagi makes it to dinner, he finds his parents have decided to resolve the hospital switch by conveniently having him marry the daughter his birth parents raised…who turns out to be none other than Erika herself! Erika feels torn-up after seeing Nagi and Hiro on a date, so she forces him to go on a date with her, too. How will Nagi deal with his new conflicted feelings? Meanwhile, Nagi’s grades have taken a hit due to his new living situation, and Hiro is about to learn a major secret… Things start heating up in this tangled love rectangle!