Kayako said: They're both girls. And.....I'm not sure exactly what they're doing, or why.
After the festival, when Minoru sees Maria's photo of her and Canaan together, Minoru asks her what she knows about Canaan. Among Maria's other weird and useless answers, she replied that Canaan's shoe size is 22.5. This apparently is explaining how she knows that... XD Quite brilliant, I say!