What do you mean by conjoined? I mean, by the looks they don't seem to be connected and sharing the same body. Maybe you meant cooperative?

 

Regarding character design, they look quite generic, which isn't bad by the way. Though I like the heroine with a cigarette, even if she looks generic overall, giving her cigarette makes her stand out a lot. I also like the walking fleshlight enemies you got there.

I can't say it is a parody of something or not or draw similarities with something because I don't watch anime that much, the only thing I can say it looks like your average jrpg party except for that they are all girls.