Excuse Me, You Just Have Said "Retired"?!

Fujino Reina, a 39-year-old single mother with a high school 2nd year student son. She doesn't think a "mother" can be in love in 40s. At the workplace where she returns on time, she doesn't want to get ahead and wants to stick to "mom". And she categorizes somethings and puts "good for the world" first. She feels calm even after raising her child, and she feels like she's already living the rest of her life. At that time, the love affair of her grandmother, who is nearly 80 years old, is discovered, and Reina makes a certain decision. After that, she meets the person she admires again! Confessed by a new employee! The calm life begins to move?!