Zelda and Sonia foot worship (Hyrule Warriors: Age of Imprisonment)

Zelda needs to train her inherent light and time powers with Sonia but things are getting kind of weird, right after the training Queen Sonia needs to check Zelda's bare soles. This is something unexpected and quite uncomfortable for Zelda, she is not used to wearing those zonai sandals and her feet get pretty sweaty wearing them, and now out of the blue, Queen Sonia wants to check those sweaty soles? And she even asks Zelda to smell her own sweaty sandals, what is going on? is this some mysthical part of the training? what does Zelda needs to learn besides her amazing feet scent?