Tomonori was overjoyed to know that his childhood friend was alive and well... except Zonghan wasn't exactly the latter.

"OH MY GOD ZON-CHAN! IT'S BEEN YEARS!"
Zonghan was happy that he had reunited with his childhood friend after all those years, but all that happiness turned to despair when Tomonori brought up the last thing he heard from him.
"So Zon-chan, how's that girlfriend of yours you told me about?"

It all came back to Zonghan, a very painful memory of what could've been his wedding.
He stood there at the altar, waiting for his bride to be to come marching down the carpet, but she didn't. Instead came in a man in a suit with a letter from Zonghan's fiancée.

"Dear Tian Zonghan.
I've seen the gifts you left me in these weeks.
I have to be honest with you. This four-year relationship has been... wonderful.
I know how badly you want to marry me, but I've found someone else, and I can't stop thinking about him, so...
I think it's best if we go our separate ways... okay?
I'm not the wife you're looking for... I can't be... You deserve someone so much better than me...
I'm sorry...

Yours truly,
鍾嘉綾 (Zhong Jialing)"

The sole fact that his betrothed turned out to be a cheater was a scar in Zonghan's heart, and couldn't get over it for quite a long time, which resulted in him gaining a whole lot of weight.