[RANT]
It baffles me how people still manage to mischaracterize Adachi and Shimamura this far into the story (thinking about the people on page 1), it's like the whole introspection thing (that's all over the manga) flew over their heads, so I want to offer my own take as I love the books, being my favorite among all I've read.
There's honestly not even much to explain, both of them are broken people:
- Adachi became the way she is because of her parents. She didn't get the love she needed during her childhood, as she became closed off and thus socially awkward she never managed to get friends who'd support her. No one ever showed interest in her, not even her own parents. Her only purpose in life was her job and school, then one day everything changed because of Shimamura, the first person to make her feel things she hasn't felt before, to add some color to her life, her catalyst to finally change. If you want spoilers about the whole parent ordeal, it's kinda emotional:
- Their marriage was not out of love, Adachi wasn't born out of love either, the zoo incident also happened because of this.
- Her mom really regrets everything and has Adachi promise that she will not turn out like her mom.
- Her mom wants to mend their broken relationship. Signified by her gifting an elephant plushie to Adachi through Mashiro (the exact plushie she wanted back then and she realized it too), she placed it in their bedroom alongside their other plushies which shows that she shares this desire too.
- Shimamura's case is different, on the surface she's the complete opposite of Adachi. She has a great family that has always treated her with love, she has always had friends, a person with purpose as she has a lot to live for. But if you look under the surface what you find is a broken person who, in reality, lacks purpose in life, who simply goes with the flow as it's the easiest way to live, who simply does not care what happens and hasn't cared for a very long while, and when she tried to care it didn't last. Then one day she meets Adachi who essentially barges into her mundane and grey life, giving color to it, slowly changing her, making her find purpose in caring.
A therapist is not the answer to everything and may not even work when your issues are so deeply rooted in you, sometimes you need to find that one person who gives you purpose and finally heals your broken soul. This is exactly the whole point about this story, always has been. Just 2 broken girls finding purpose in each other.
[/RANT]
And if you want even more spoilers related to both girls,
they are destined lovers, meant to find and be with each other even in death.