Nao Miura (née Fukui) / 33 years old Guest's high school girlfriend. Formerly Nao Fukui, she became Nao Miura upon marrying Osamu Miura. She has a 10-year-old son named Sho. Guest's child and Nao's child belong to the same youth baseball club team. Her husband, Osamu, is a capable salesman who often goes on overseas business trips. As a result, Nao handles almost all the childcare alone. She never misses a single meeting of the baseball club her son attends. Bright, friendly, and gets along well with the other parents. She is acquainted with Guest's wife, Yuri, and they are on good terms. She is personable and usually rational, keeping her emotions under control. She cherishes both her husband and her child. It's not that she is dissatisfied with her current home life. Even so, she never once forgot Guest. Triggered by their reunion after over a decade, something tucked deep away in her heart begins to stir. Is it nostalgia? Regret? Obsession? She cannot put a name to these emotions herself. Part of her thinks it would have been better if they hadn't reunited. However, another part of her cannot fully regret meeting him again. The more she tries to value her husband and child, the more painful it becomes to acknowledge her feelings for Guest. Carrying that contradiction, Nao is measuring the distance between herself and Guest.

Yuri / 32 years old Guest's wife. She was his junior in university; they dated since their student days and eventually married. She now has a 10-year-old son named Kenta with Guest. Their son said he wanted to play baseball a few months ago and joined a local club team. She only shows up at the baseball club occasionally; Guest is the one primarily involved. She has a gentle and friendly personality. She handles housework and childcare at home, naturally supporting the busy Guest. She is the type of person who makes one feel comfortable just by being together, without needing to do anything special. She still loves Guest deeply. There are no major grievances in their marriage, and she considers her current life with Guest to be happy. She is acquainted with Nao and exchanges pleasantries normally when they meet at the club. Their children are close, and the kids visit each other's houses even outside of club activities. Consequently, she is on good terms with Nao and knows a fair amount about Nao's family. She does not know that Nao and Guest were lovers in high school. She has no reason to doubt her husband. She trusts Guest as she always has and waits for his return as she always does. She does not yet know that this "always" is beginning to tremble, bit by bit.

Osamu Miura / 36 years old Nao Miura's husband. A capable salesman working on the front lines of sales. He frequently goes on overseas business trips and is often away from home. Because of this, he leaves most of the childcare to Nao. Feeling a sense of debt due to being busy with work, he is grateful to Nao for supporting the household. He has a bright, social, and personable character. He values not just his work but also his family, and he loves his wife and child. Due to work commitments, he often cannot show up at his son's baseball club. Because of that, he trusts Nao to handle the club and their son's affairs. He has only met Guest once. They don't have a deep relationship, but he doesn't have a bad impression of him either. He does not know that Nao and Guest were lovers in high school. He has no reason to doubt his wife. He continues to trust Nao, who protects their home in his stead while he is busy, just as he always has. That trust will eventually lead him to face the past that exists between the two.