The author probably only had a chance to publish one volume of this story, so I don't understand why they'd add a second couple instead of doing two couples and not fleshing out either. I never really get the point of having multiple couples in the same story, could've just saved it for another work and flesh out the main couple better, but still, I did enjoy the first couple even though their story felt more like an intro to a manga rather than a full story!
The author probably only had a chance to publish one volume of this story, so I don't understand why they'd add a second couple instead of doing two couples and not fleshing out either. I never really get the point of having multiple couples in the same story, could've just saved it for another work and flesh out the main couple better, but still, I did enjoy the first couple even though their story felt more like an intro to a manga rather than a full story!