[Solved]-Tooltip doesn't show properly in highcharts-Highcharts

the diagram itself doesn't have any problem

actually it does, as you have set the value x=10 two times. therefore, it's not mathematically a function and this maybe is preventing it to render the tooltips correctly. i changed it and the tooltips seem to work fine (displaying the following information: 'tokio', y-value in bold and x-value at the top). example

caution, extreme hackery ahead: you can create more than one series on a chart so you could do something like this. using 2 series. of course the curves are not properly matched but it gives you a starting point.