Here are the different established relationships of Zaguān with the other characters, during the course of the publication of manga.
Zaguān introduces Legoshi to the life and mindset of seafolk while visiting Sea District 3, as he almost gets devoured by fish Porikokos out of misunderstanding. He describes the life cycle as fated by the ocean and that "predator" isn't a word used.
He teaches two key phrases that end up saving his life in Chapter 141ー"Daba-baba Legoshi ponpo-robú" (My name is Legoshi) and "Agaga papubu daba goma bída" (I am friends with a spotted seal).
Seven and Zaguān have friendly interactions. It's implied that she's the first of the Hidden Condo residents that he met. They were both present with Legoshi when he put up the invitation for a rooftop rice-cake roast. What Zaguān and Seven share is their mutual friendship with Legoshi and concern for his well-being.