I have been holding this off till know knowing I would be argued oblivion.
But these girls. Especially Tomikawa needs to get some professional help and therapy. They are sweet together and all. But that kind of mental burden will inevitably cause some issues and hardships down the road. No matter how much good they want for each other.
I won't argue that they don't need therapy. But I will point out the fundamental problem with their situation is neither is in a good place to seek out or receive therapy, especially with the state of Japan's mental healthcare system. Tomikawa would likely need her mother's permission to enroll in therapy which isn't happening while her mom won't even acknowledge her existence, and whatever is up with Hiiragi's home life she's not exactly in a situation where she can easily reach out - if she even had the impetus to do so.
It sucks but the best place for them right now IS with each other, if only so they can help each other not go out and jump off the nearest building.
Edit: To expand on this thought somewhat with Tomikawa, a huge problem is nothing her mother is doing can realistically be defined as abuse or child abandonment under Japanese law. She is providing what she is legally required to by the state - food, shelter, clothing, education. In addition, while Tomikawa dresses and acts like a gyaru girl, she isn't actually a delinquent by any real measure. She attends class, is clearly smart and gets good grades, plays by the rules, and hasn't gotten into any real trouble. Because of this, it's unlikely for the school to request she speak with a counselor or anyone involved with troubled youths. And because Japanese law generally dictates that matters within a household are the responsibility of the household, police and child protective services wouldn't get involved unless there was evidence of physical abuse or child neglect taking place.
Tomikawa could get police involved by engaging in delinquency that would gather the notice of law enforcement, but that might not work and would also likely end up on her criminal record, which might affect future job or school prospects. If she does want to go to a good school and get a good-paying job in the future, she just has to put up with it long enough to move out of her mother's house. Otherwise, the only other recourse that she feels is available to her is, well... suicide. Which is how a lot of people end up in that situation. People don't know anything is wrong with a child right up until they jump off a roof, then suddenly it comes out how awful their home life was and everyone acts like they always condemned it.
For the time being, the best thing for Tomikawa is the thing that will keep her from taking her own life... which is, morbidly enough, Hiiragi saying she'd die as well. It's not healthy, but it's more than nothing, and nothing is what she gets from her mom.
Ahahaha no, we are a WAYS away from this ride being done with.