Katagiri Teppei, an advertisement designer who is transferred to the Sales Department and is forced to adapt to the new working environment. He checks in to a hotel with Uesugi Riko a night before but forgets about their encounter even when he sees her again in the office. They get off on the wrong foot and things always get heated between them. But an unexpected turn of events helps them both say goodbye to their pasts and move forward.

Teppei doesn't seem to like working in the Sales Department, so the section chief gives him an important project to test his capabilities. During the course of the project, he offends other colleagues unintentionally and receives retaliation. Meanwhile, Soichiro finds out that Teppei and Sanae dated before.

Teppei goes over to Erika's house but their plan is interrupted when Riko shows up there. Erika tries to get Riko to confess about her feelings for Teppei. On Teppei's birthday, Soichiro asks to have a meal together and sends Teppei to wait for him at his house. However, Teppei runs into Sanae there and things get awkward when Sanae talks about her being his sister-in-law. Left in disappointment, Teppei finds Riko waiting for him near his house area.

Riko gets sick and Teppei makes porridge for her. Teppei and Riko bond over golf. Meanwhile, Soichiro and Sanae complete the betrothal gift ritual. However, Soichiro meets someone from his past, and he seems to be having doubts about getting married.

Soichiro rushes over to help Nami when he receives a call only to end up being sucked into a trap that she lays down for him. Teppei and Riko, on the other hand, are at odds again. And just when they are about to be on good terms, things take a turn for the worse when Teppei stands Riko up to be with Sanae.

Teppei and Riko are finally together. They're trying to keep a low profile so that people at work don't find out about their relationship. Teppei officially introduces her to Sanae and Soichiro as his girlfriend. Meanwhile, Sanae is having problems with Soichiro and she has a heart-to-heart talk with Teppei.

Sanae finds out about Soichiro's affair with Nami. Nami thinks that she'll be able to make Soichiro suffer like she did, but to the contrary, he chooses to give up everything for Sanae, which is something he never did for Nami. However, the damage is done and Sanae is put in an awkward predicament when her classmates bring up her wedding. Riko, on the other hand, finds out that Teppei hides something from her.

Teppei is in charge of another ad campaign and there are colleagues who refuse to work with him again. Meanwhile, Sanae and Soichiro continue to have problems. While Teppei and Riko's relationship seems going strong, Teppei becomes Sanae's confidant and becomes closer to her. Soichiro's friends are throwing an engagement party for him and Sanae, and he ends up attending alone.

When Riko returns to her hometown, Teppei wonders if she'll even come back to Tokyo. When he learns from Erika that Riko will soon be back, he waits for her at the subway station and reassures her that she's the one he loves. Teppei promises Riko to clear things out with Sanae and give her a call after the meeting. However, Riko waits all night but the call never comes. Just when she's feeling lost and alone, she recalls what her dad told her and decides to take his advice to return to her hometown.

Riko keeps having doubts about Teppei. She has made up her mind to go back to her hometown, Nagano, no matter what Teppei says. In order to end of good terms, they have decided to spend her last day in Tokyo together. Meanwhile, Sanae has decided to go to China, but Soichiro wants her to stay.