People are calling this "messed up" and "a complex" because this isn't a healthy relationship. If it's not obvious enough on the first readthrough, "Only one person in the world was 'family' to me" appears smack dab in the middle of the page where she falls in love. As I said, this is right as she finds something permanent; the story makes a point of taking everything else away and "A Love Smeared In Ashes" shows us just how much abuse she'll take without complaint, with her only "snapping" out of pure possessiveness.
Now, the author clearly presents it as a sugary-sweet explanation of what set Sunako's heart aflutter. However, this isn't some sort of death-of-the-author analysis that's going on: we're not seeing blue curtains and reading endless amounts of imagery into them. What we're doing is quite literally looking at it literally, looking at the pieces the author presents us with and figuring out how they fit together, which isn't as happy as the story presents itself as. (I will float the idea, however, that the story is deliberately multilayered and what we're seeing on further analysis was put there intentionally)