Akiha Okado is a designer who loves her job and is content with being single for the rest of her life. Her friends often ask her when she will get married, but she enjoys her carefree life. One day, Akiha meets Shu Momose at a party. He bombards her with questions about marriage, before suddenly asking her to marry him. Furthermore, the type of marriage he proposes is far from normal. Akiha is enraged at Shu's preposterous request, but at that moment she learns that her grandmother has collapsed and ends up going to the hospital with Shu. At the hospital, Shu tricks Akiha’s grandmother into thinking he and Akiha are dating. Then, he even starts taking marriage registration forms out of his bag. Not wanting to risk causing shock to her grandmother, Akiha is at a loss as to what to do.

Two weeks have passed since the start of the faux marriage. Akiha's slovenly lifestyle clashes with Shu's orderly personality, and she reaches her wit’s end when Shu complains about her capsule toy collection. One day, Shu’s brother Asahi visits their home and asks for help preparing boxed lunches at his shop over the weekend. Shu is busy with work, so Akiha volunteers to help in his place. It is Akiha’s first time visiting her in-laws, and she is overjoyed to find that she gets on well with her brother-in-law’s wife Miharu. Akiha is not good at cooking, but she tries her best to do what she can. However, despite her best intentions, she makes an irreparable mistake.

Akiha feels uneasy after learning that Shu is in love with his brother’s wife, Miharu. Amidst this, Shu’s former junior high school classmates host a wedding celebration for the couple. Miharu and the old classmates are enjoying reminiscing, when Shoko Mamiya, who just happens to be passing by, joins the party. Then, Akiha’s meddling rubs Shu the wrong way, causing him to close off his heart, and making the atmosphere at home awkward. Akiha learns of a big upcoming competition, but she cannot talk about it with Shu because he is in no mood to listen. Then, something happens that leads to an unexpected development in the competition.

Shu is overjoyed when a friendly hug leads to him making his first female friend. He grows so fond of Akiha that he even completely ignores the rule he made himself about not using each other’s tableware. Akiha is bewildered by Shu’s attitude as he delightedly repeats the word friend. Shu invites Akiha on a day trip to a hot spring inn. Akiha worries over her unreciprocated love for Shu, but decides to go because they are friends. However, Miharu and Asahi show up on the day of their trip.

Miharu leaves behind divorce papers and vanishes. Shu tries everything to find out where she has gone, while Akiha can do nothing more than look on worriedly. Miharu eventually reappears, saying that she does not want to return home. Shu then offers Miharu a place in their home. However, this leads to major changes for the pair in a faux marriage. Akiha feels tense while sharing a bed with Shu, who begins to open up about his feelings for Miharu little by little. Miharu living in their home begins to cast a shadow over the pair’s relationship and Akiha senses that her desire to be with Shu is in vain.

Akiha realizes that she does not stand a chance of being with Shu after witnessing his unreciprocated love for Miharu. Nevertheless, Akiha is determined to preserve their relationship as a faux married couple. A massive panic occurs when Akiha’s parents show up at their home. Their appearance brings about a sudden development in the debt problem connecting Akiha and Shu. At work, Akiha receives a request to design a book cover for an author she admires greatly. She jumps at the opportunity and immerses herself in work, but for whatever reason she gets more and more distracted. Furthermore, Yuito Makihara suddenly declares war on Shu, causing Shu to do something that goes beyond the bounds of friendship.