On that day 5 years later, when my wife returned home.

Five years ago, Miki, the wife of Furumachi Tsubasa, engaged in infidelity and left him.  Five years later, she shows up at his doorstep with nothing but a single piece of roller luggage, and a four year old daughter, begging for a place to stay since she had nowhere else to go.  Failing to close the door in her face, the couple who had failed to divorce in that time are once more living together, struggling to come to terms with their regrets, and the damage which was done that could never be fixed.