While I am sure everyone has seen and watched the episode I am referencing, I have marked this as a spoiler for some obvious reasons.

Something stood out to me the second time I am watching the series. I have watched a fair bit of romance / slice of life anime at this point and while I am not an expert on Japanese culture or interactions... Arima gave a fairly round about confession to Miyazono in the field of fireflys. "I had you in my heart." Given the Japanese culture of not directly confessing or being open/honest with feelings this would have been seen as a pretty big deal to Miyazono under normal circumstances (IE her not being terminally ill). So, she does not respond directly but tacitly gives approval for him to proceed (by not outright rejection either). The mother esq figure/mentor of Arima - Seto - within 5 minutes figures out he played his heart out for a woman and read Arima like a book.

Miyazono does not respond to his obvious ploy but starting in episode 12 she becomes extremely active in Arima's life, and you begin to see him look and act differently. Doubly so when around Miyazono. Watari and Sawabe both notice starting in episode 12 that the two of them are much-much closer than they should be considering she is "dating" Watari. Miyazono even says that Arima has grown taller now that he no longer slouches. Miyazono's parents literally fawn over and talk up Arima to the point that they are cool with him being around their daughter, another huge step in a relationship in general for a young couple in high school. Again, tacit approval from the parents.

Does anyone else see how much of a "confession" this might be or am I reading too much into it? We know that Miyazono really does love Arima as told at the end of the series. I feel this was the moment the two of them secretly solidify their position in one another lives, for better or worse, despite the messy dating situation (much to Sawabe's ire and Watari's care free attitude not withstanding).