It's the story of two sisters, Ume & Kame who collect discarded objects from rubbish in their town. They care for these found objects and one day they find some red yarn. That night, they are roused from their sleep by the sound of the rubbish heap collapsing and are surprised to find a girl knitting a sweater from the red wool. They name her Aminaoshi and in the following days, she continues to knit obsessively as the other foundling objects mysteriously come to life.
To see the trailer on the official site, go HERE and select the fourth option in the bottom menu. Here are some more stills from the film:
Mari Fukuhara's song La Lune:
Sundance Mai Tominaga Bio
Wool 100% official site (Japanese)
Twitch Article on Wool 100%