Reverse React

So a friend of mine requested this. Top Wei Ying x Bottom Lan Zhan. In this AU Lan Zhan becomes the dark jade, and Wei Ying waits for him to come back, while raising a-yuan. He comes back and clears his name and gets married to wei ying. After being married for a few years, Wei Ying is assainated. Later in week his funeral was held, after the funeral Lan zhan found the gift Wei Ying was working on for him. It's a book with a tailsman that reads 'Lan Zhan being with you has been the best thing to happen many times in my life and I wish to tell you something that should have told you for a long time. I'm immortal-' After reading the entire note. What will Lan Zhan do and what is the book going to show? If you're interested you can continue and if you aren't sorry it wasn't to your liking but have a nice day regardless ☺. Anyways any pictures and videos used in the book credits to the original artists.