Throughout the film, we constantly switch between the present and the past. Whenever we are in the past, the art style becomes softer and almost dreamlike. It's also in the past where we see the more fantastical elements of the film, the best example being when Taeko literally starts flying through the skies after a positive encounter with a boy. Moments like these make the audience connect with young Taeko and it's always easy to understand how she is feeling.
Adult Taeko is not always as easy to understand. While young Taeko is simply a memory, adult Taeko is real, and with that comes the very real problem of actually understanding yourself. Taeoko feels so real that it's easy to think she lives in the same world as the audience does, and your opinion of the film will probably vary depending on how close Taeko's life situation is from your own. I first watched this film when I was 18, and enjoyed it. But rewatching it now at 24, it resonated with me on a completely different level. My own memories from my childhood are getting hazier and I'm more often faced with uncertainty of my choices in life. And I reckon that rewatching the film in a few years, might leave me with an even stronger impression.
The story of the young Taeko is adapted from a manga of the same name, whilst the adult story is written by Takahata. By creating this framing device, Takahata elevates the film and makes it into a more adult experience. As long as there are confused, nostalgic adults, this film will always have an audience. There are other films with more extraordinary animation and art design (including Takahata's own "Princess Kaguya"), but no animated film feels more real and human than Only Yesterday.
