Which one, because I have a few 😅 Heathrea is my main yume though, and prolly they have the most of lore. So.. here's one about them (not sure if I ever mentioned it):
Despite Rea's dislike for coffee, she allows Heath to make her some once a while...and it's actually the only coffee she enjoys. Heath had no idea about it for a long time as she was hiding the fact she dislikes coffee (yeah, she was suffering to make him happy, ahahah) - Cain has told him by accident. Since then, when he makes himself coffee, he makes tea for Rea, unless she asks for a coffee.