Is there any serious romance in No Game No Life?
No, No game no life is not 'romantic' in the way plastic memories and your lie in April where, the emotional touching way.

No game no life focuses a lot more on a 'comedic aspect' of romanticism, and over the top brother sister love. And all though this is a red line throughout the series, the games they play have the bigger focus in the 'serious' parts of the series.