[SPOILERS] Yes, it’s really an HEA
To be classified as a romance, a book must end with an HEA (happily ever after) or at least an HFN (happy for now). Simply put, that generally means that the main couple needs to end up together—in a committed relationship, living together, getting engaged or married, expecting a baby… there are different ways to show that they’ve found happiness together, but that “happiness together” thing is key. Now, a lot of romance novels (like a lot of novels, period) also have subplots. Maybe the main character is struggling at work or school or with family issues. Maybe a supporting character is also looking for love. There really aren’t any genre rules that say those subplots all have to end happily… but at the very least you want a romance to end in an overall uplifting place, so even if the characters don’t get what they initially *think* they want, they still tend to end up with a satisfying alternative. But what if a romance includes something that can’t be fixed? (Or at least, that can