In one chart it isn’t possible. However you can achieve this by using two charts, one plotted on top of the other. First create the area chart and set the layer to normal. Copy / Paste this one and modify the style to line chart and modify the expression to your needs. Set the position of the expression axes to the right and set the background to transparent. Set the layer of the line chart to top.
Then move the line chart on top of the area chart and keep the size of both charts the same.