A2Z — Season 1

Natsumi is an editor at a major publisher and her husband, Kazuhiro, works at a rival company. After 8 years of marriage, they have no children, and Natsumi still uses her maiden name. Little does she know that young postman Naruo stares longingly at her every time she comes by. One night, Kazuhiro makes a confession: He is having an affair with Fuyuko, a college student.

Natsumi and Kazuhiro, post-separation, bump into each other at an author's funeral. The two have dinner, reconnecting over work, books, and many, many drinks, ending with them in bed together.The next day, Natsumi's best friend Kyoko ask her why she'd get back with her husband despite having a new young lover. Natsumi makes a bold decision.

Natsumi is at work when she realizes she left her phone. At that very moment, Naruo rings her and Kazuhiro, who dropped by the house, picks up. Kazuhiro grows suspicious. Why was the "post office" calling Natsumi? Later that night, Natsumi dines with colleagues at the office as Kazuhiro strolls in unexpectedly with Shohei, an up-and-coming author.

Natsumi is exhausted from working non-stop but finds Naruo's presence comforting. Anxiety worsens when Director Fujii wants her to secure Shohei's next novel, even if that means blind-siding Kazuhiro. Natsumi loves Shohei's talent and yearns to work with him at any cost. Natsumi fumes when she finally gets home to find Kazuhiro relaxing in the bath.

Natsumi visits Naruo at his house. Kazuhiro calls out of the blue. Natsumi doesn't pick up, but still rouses Naruo's suspicions.The next day, Natsumi tries to persuade Shohei to write his next piece for her. He repeatedly avoids the subject, to Natsumi's frustration, which worsens when Kazuhiro texts her the next day to press her on why she didn't pick up.

Kyoko tells Natsumi she saw Kazuhiro and Fuyuko at the movies. Natsumi is curious about the girl, and wonders how she compares to Naruo. Director Fujii presses Natsumi to pursue signing Shohei, telling her to "teach Kazuhiro a lesson."When Kazuhiro announces he will be spending the holidays with Fuyuko, she accepts the news with a stoic face but a broken heart.

Natsumi runs into Kazuhiro at an author's end-of-year party. Unexpectedly, Kazuhiro does an about-face on his previous plans, saying he doesn't want to divorce her and wants to spend Christmas with her instead of Fuyuko. Natsumi rejects him with a smile.On Christmas Eve, Natsumi brings fancy ingredients to Naruo's apartment, where they throw a modest party for two.

Fuyuko calls Natsumi's office and asks her to meet up.Despite being a homewrecker, Fuyuko is bold and unapologetic towards Natsumi, plainly telling her she should leave Kazuhiro. After saying her piece, Fuyuko quickly leaves.Meanwhile, Kazuhiro is drinking at a bar by himself, remembering the young postman he met earlier in the day.

It's spring, and Shohei's book is published. Natsumi runs into him at a bookstore, and they grab soba together. Things become tense when Kazuhiro and Fuyuko walk into the same restaurant. Shohei lets slip that he has plans to work with Natsumi. Kazuhiro confronts Natsumi about it at home, leading to an intense argument. Natsumi must face the hard truth that her romance with Naruo is fading.

Kazuhiro splits up with Fuyuko. Natsumi tells him that she is in love with someone else and can't live with him anymore.She moves in with Kyoko and starts visiting Naruo every day. Before long, it's summer, and Natsumi runs into Kazuhiro again at an awards ceremony. When the party ends, she chooses to visit Naruo instead of going out with colleagues. Is this really the life she wanted?