Kanae is portrayed as this crazy person one bad day away from killing everyone, but really she is the most human person in this book. this is what goes in the mind of a person who doesn't believe they deserve kindness, they self destruct, they get ugly, they make bad choices to avoid pain, they conform to avoid ridicule because someone other than yourself hating you is the worst thing in the world.
She never really trust Hiroshi nor cared for him at first, even after she was told she "may be" in love with him, her heart was always on the fence about it. Only when she had the company and acknowledgement she was looking for, she realized he was an eccentric part of her life. Whenever his kindness was taken for granted, it hurt her the most, someone who was a void of kindness seeing others treat his dedication like happenstance.
this book may be going for how everyone else is using Hiroshi and how it butterfly effects their peers. I believe its going towards a direction where Kanae finds her own love for herself and become the first or last one who no longer needs Hiroshi to love her for her when Hiroshi begins to need her, just a few chapters ago she was posting a stray cat she liked on Instagram trying to figure out who she is
id like to also add that Hiroshi didn't "save" her. he offered her consistent affirmations and moral support. the delinquent guy thought he saved her, where he end up? He wasn't confident he'd get with her which is why he participated in the kidnapping to begin with and got frustrated it didn't work. Hiroshi went the extra mile while other guy was waiting for opportunities to get with her than to actually see she needed help. never asked her what she needed otherwise she wouldn't be selling her body to pedos, he knew and let that happen