Suwako Moriya is the original goddess of Moriya Shrine. She is not actually a goddess of frogs.

Her way of speaking is undignified and she looks rather young for a god, but her carefree attitude may actually be a fairly accurate representation of deities in Japan.

Snakes beat frogs but lose to slugs. Frogs beat slugs but lose to snakes. Slugs beat snakes but lose to frogs.

Snakes, frogs, and slugs. A so-called three-way standoff. This is definitely related somehow to belief in the Mishaguji, curse gods in the shape of large white snakes with red eyes and mouths.

There is historical evidence across Japan of native gods being invaded by new gods and having the base of their belief stolen from them. However, this was not a religious revolution. The changes were established slowly, with various tactics. It was like how a snake coils itself around its prey.