Yanagi Renji told Sanada very early on that this was his heart disease and Sanada couldn't cure it, even if Sanada was the main source.
The story begins with the entanglement between Sanada and Yukimura.
If Sanada didn't like Yukimura, then he wouldn't have met Yanagi Renji that time.
At the end of the story, only Liu Renji is still struggling.
You are afraid of love, so you come to me and tell me that you lack love. I am in love miserably, and after all the hard work, I am afraid that you will leave again.