[Coldsaturn]

The little fish also appears when you interact with him in the Cafè, going for the Gift option. And also in cards and events.

Yup you remember right, in Nightly Strolls Raf asks MC to swear that she won't disappear on him again (ouch after the myths), and he says:
"This is a ceremonial vow of my people. Fish are the emissaries of the ocean. If the vow has the blessing of the ocean, then a fish will appear between our palms."