I believe that most Japanese movies and dramas have a sprinkle of quirky flavor to them. No Japanese story is without it. This story is no different in that, but it also compels the viewer to think beyond what they're shown.
I found this more of a woman's story about personal struggles in a society that pushes a particular set of goals on women which mark a successful life, making marriage and children milestones and the only life goals necessary for women. Misogyny at its best.
The female lead (FL) is encouraged to achieve these life goals, but is somehow thwarted each time she makes progress. Her family belittles her few achievements and ignores her dreams. Her boyfriends disregard her desires and needs completely, focusing only on themselves. Throughout her life, she's told that what she wants doesn't matter in the real world. She's shamed to want anything for herself. The sense of melancholy is heavy in and around her. It's as though misfortune follows her everywhere, causing her misfortune.
When she meets and befriends a person who shares her dream, he's forced to stop doing what it is he loves due to unknown obstacles. In the sadness of that event, she finds a new friendship and exciting romantic partner; which is technically illegal. She chooses to hold onto a moment of happiness. The moment is soon disfigured by reality and personality conflicts, which she faces alone despite having a number of people in her life. In the end, her struggle is a culmination of her acceptance of others' adverse treatment of her. Once she realizes this, it's the end of the show.
The movie inside the series works as a reflection of the society she lives in and her own development within it. It's cinematically beautiful and disparaging. It's the disease within the perfect body.
TL/DR: The FL earns her independence through relationship turmoil and professional difficulties.