I understand Oshimi and his expression of fixation and confusion in this story. I feel bad that Oshimi's work might be mistaken as a comedy (similar feelings with "Devil Ecstasy"). Because it is so absurd or out of the ordinary and so extremely fixated people don't take it seriously.
People might say Yumeko is a bad person for her actions, while it's true I think it is important to look at her as a character, an expression, and a method of storytelling. She's selfish because she's trying to understand a phenomenon in her head with no regards for the fact that said phenomenon is a deeply personal thing to people. Because she is so hyper fixated she doesn't really understand this which isn't an excuse for her, I'm saying that's the story and circumstances that lead to the ultimate message. She doesn't see a dong as something that should be attached to a person like when she does the portrait of him. He wants to see it and seems to be expecting a drawing of himself but it all comes out as abstract shapes. It's all about the idea and Oshimi captures this fixation greatly in something like that simple and abstract phallic shape. Through just this shape repeatedly Oshimi captures so much emotion, mystery, confusion, consumption, and passion. I can understand and relate to Yumeko especially after knowing Oshimi's life experiences.
I fully believe him when he says this is a reputable coming of age story because I see it in all of it's crude beauty although others might not take it seriously. Oshimi's early works remind me of a drawing which you would see carved into a middle schooler's desk. In his lines and in his expression. I like that they are raw and extremely expressive in this way. I love his work and it's great to see him evolve his expression from crude stories like this to being able to express himself through deeper psychological plots too.