People really out here outing themselves for wanting an actual romantic relationship between 34 YO woman and a 15 YO boy.
Ultimately, it was a story between two people helping each other through their own personal problems and trauma while navigating the social intricacies of an age gap. Romance shouldn't come into because *spoiler warning* it's a crime. The relationship wasn't going to end, but the manga would so I'm not really sure what people were expecting, aside from maybe an explicit "mother/son" declaration, which would have run counter to the ultimate point of the story.
Relationships can be complicated and sometimes they can't be properly defined in a simple statement or category. This manga explores those complexities and it does it well. Anyone sad that it didn't end with an illegal relationship between a literal child and adult should probably consider not actively rooting for pedophilia.