beta
basically onaga is a conventional cute girl with everything going for her and she should be happy as she says in the beginning, but we clearly learn she isn't and instead she feels hollow because everything in her life is "good' but monotonous. She doesn't have any real passions or close relationships, and is shown staring silently at the functional families and friend groups that sit at her job.
Kawashibara is the exact opposite, he is not conventional at all and a social pariah but he has the one thing she doesn't; genuine passion and a clear soul whenever he dresses up in girls clothes and does girly things. Onaga lives vicariously through Kawashibara's happiness by providing him with girly things like makeup and clothes. She enjoys being responsible for his happiness and can find purpose by delivering these small joys to him.
When she learns that he wants to confess to somebody and actually move forward with his life instead of staying her plaything, she lashes out and says that she was the only reason he got thus far; and that she is the harbinger of his happiness and without her it's impossible.
obviously he gets rejected and now onaga can be his deity once again and she wins in the end ig