@Nihilist1 A series is not defined solely by its premise or the common trope it uses. It's about the execution.
If you're talking about the similarity of a trope, then you can say that ReZero and Konosuba is similar because both of them are isekai anime, while clearly it's not the case. The tone, the plot, the characterization, almost everything about them is different.
So, to say that all this series has is the trope "someone with high status missing family" is just an extreme simplification. Even though both Sangatsu and this manga uses similar trope, both manga has so many differences. And personally, I think there are more differences between both manga than the similarities. Both manga has their own unique strength.
If you want to know, I enjoy this manga more. Sangatsu is just too boring for me...