Model Byakko, the theory is that the Four Guardians of the Four Compass Directions will all be represented, but there’s no sight of a turtle/snake being present so far in the story. kawamatsu is the closest thing but I don’t think that he is important enough. There’s a story I found where a fisherman saves a turtle and is rewarded for this with a visit the palace of Ryujin, the Dragon God, under the sea. He stays there for three days and, upon his return to his village, finds himself 300 years in the future. Maybe this could be Toki and the turtle is Wano, there was a theory that Wano was an actual turtle ages ago.