My stepmother is my ex-girlfriend.

One day after coming home from class, Najima hears his father Teruo talking to a woman in the living room. Don't head into the living room thinking you've got a new girl. Teruo introduces his new woman to his son. As soon as they greet each other half-heartedly and make eye contact with their father's woman, they are speechless. Her father's new woman was Rie, a college classmate whom Nazima dated two years ago. She met Teruo, who worked at a bar to earn money after her father died and her mother collapsed. Speaking of which, I recall the old memories of Najima.