No guarantees I got all names and titles correct. Even on the official site, there doesn't appear to be a character guide yet.
Thanks!
Gingkohime-no-Mikoto (Shirogane/Kogane)
Two tiny sisters who have just been born among the goddesses who protect breasts. As they have no shrine, they may or may not live under Shinka's breasts. They are always concerned about the breasts of Shinka and others around them.
However, the princess-miko's breasts are apparently very popular even among goddesses who protect breasts, so these sisters can't seem to get them off their minds....
They sometimes have sisterly quarrels, as their preferences in breasts differ.