It's not a sad ending as far as I remember??? They do reconcile at the end. I can tell you what happens but are…
Ok so basically their relationship gets found out by the school, friends and the parents. And Sheng Wang's dad tries to send his son abroad but Jiang Tian intervenes and goes abroad instead with his mother (who is mentally unstable). Then there's a timeskip. Now this part is kinda sad. But they meet again albeit by accident at a dinner. Jiang Tian's a scientist now back to China and had some collaboration with Sheng Wang's company (as far a I remember). And then it's all yk warm and fluffy. They get together, let their parents know, reunite with their friends from hs. And it ends with them visiting their former hs