Yesung enlisted in may 2013. He sang his latest solo song, "Gray Paper", at the only SS5 he could participate in before enlisting.
Some months later, something happened in SS5 Tokyo (130727): Kyuhyun and Ryeowook sang Gray Paper (fancam).
And after the song...
Ryeowook: "Kyuhyun was the one who came up with this idea of performing Gray Paper"
Hyukjae: "So Yesung didn't know about this?"
Kyuhyun: "I only told him there would be a surprise for him"
cr: siohappy
Kyuhyun: we were thankful about KRY receiving lots of love in Japan, so we prepared an event (to make the stage look like we are singing w/ Yesung)
Ryeowook: Kyuhyun-ssi planned this stage
Eunhyuk: But the important part is that Yesung-ssi doesn't know about this, right?
cr: NKsubs
...so singing Gray Paper was Kyuhyun's idea.
Yesung posted the link of the fancam on Twitter saying :
俺を泣かせるなんて! ありがとうございます。^^
It made me cry ! Thank you ^^
Fancams of the second day (130728): here and here ; members talking about Yesung here. And here's the HD version from the DVD:
Sungmin : Gray Paper was Kyuhyun's idea!
Kyuhyun : It was secret for Yesung. Then I talked to Yesung last night, he just said one word, it made him cry.
cr: wwmisa
Kyuhyun was doing the 'dont mention it' action when Wook said the project was his idea
cr: morningsuju
And then, some fanaccs of fans at Mobit :
My friend tell Yesung that Kyuhyun was tearing at last night’s SS5 Tokyo… He replied “Ah~ really? its too hard to see Kyu tearing”
cr: kklee1995
Did you know that Gray Paper was Kyuhyun's idea ?
Yesung replied “Ah~ yeah, I don’t even know that Kyuhyun will be sweet and care about me…”
cr: kklee1995
Kyuhyun: Do you miss Yesung?
Fans: Yes!
Kyuhyun: Do you know Yesung?
Fans: Yes!
Kyuhyun: Who is he?? (And then curls his fingers to imitate Yesung's small hands)
cr: kikiikyu
--> fancam here
And it's been said that Gray Paper will be performed at all the future SS5!
Siwon: Do you guys miss Yesung?
Fans: yes!
Wook: The stage we had just now that performed with Yesung was actually Kyuhyun's idea.
Hae: How did you come up with this idea?
Kyu then got all shy and used his hand to make a gesture like 'don't talk about this anymore'.
Hyuk then said '你不是不喜欢艺声吗 (Don't you dislike Yesung)?'
(Kyuhyun then went over to stop Hyuk from saying more, and then return to his spot)
Kyu: actually Yesung hyung really wants to be here on stage with us. So, want to sing together with Yesung hyung on stage for everyone. What do you guys think?
(fans clapped)
cr: siohappy
--> fancam here (1:30)
Kyuhyun wanting to stop Eunhyuk from saying more