Hata no Kawakatsu, who created Kokoro's masks, was conflated with Matara-jin, the god Okina is based on, making Okina Kokoro's parent as the creator of her masks.
Also to get the point across even more, Okina's first name sounds very phonetically similar to auspicious old man mask from Noh theatre which is also pronounced as Okina and that mask in particular is said to be based on Kawakatsu's own face (this mask is also often used as goshintai for Matara-Jin).
