If you go to the lake where Susie and Noelle talked at in chapter 1, an onion octopus comes out of the lake
You can return later in chapter 2, and I never checked in chapter 4 but I'm pretty sure they disappeared, the theory states that in chapter 5, during the festival, one of the vendors you can buy from sell onion flavor tentacles if I remember correctly
They cooked my boy Onionsan