Oh! I know that feeling (assuming this isn't an actual confession lol)! Finding someone you just have a kind of CONNECTION with, that just kind of clicks. It's not quite family, but it's just as intimate and yet different from romance. I always thought of it as like a "Kindred Spirit" kind of feeling, but Soulmate would work - though more of a Soul-"Mate" lol.
I love this series so much, and I'm so happy for Iruma who has grown so much.