I also really like this idea and I think it would be the perfect thing to make Haruki feel at home with Amiko and the other guardians. His lack of a nurturing mother and all would leave a void in his life that they could fill.I have this thought in my head. I'd like it if the guardians all had a meal tradition, at least around Suvon. Growing up around animals, Suvon had to fight for his meals, so now, whenever he sits down to eat with anyone, he steals their food from their plate. He does this Every. Single. Meal. To the point that I think it'd be funny if the Yokai had gotten in on it. So now it is common for the guardians and those who know him, to guard their food at meal times, and is considered a right of passage to people new to the group.
Suvon also has an unfair advantage in that he can use two hands to steal food and use his tail to defend his own. For some reason, the idea of him using his high speed capabilities and stealing food all the while looking nonchalant is just so funny to me.