Okay, this took me a bit, to tell the truth... XD But I think I'm now able to summarize what I understand by carefully observing for a year. =w=

From predebut until Showcase, 2012 - Junmyeon looks for Jongin; Jongin cooperates.

June 2012 - Junmyeon is still looking for Jongin; Jongin rejects him.

July 2012 - Jongin changes his mind; Junmyeon cooperates and KaiHo begins*.

Aug/Sept/Oct/Nov 2012 - KaiHo goes on, with ups and downs; Baekhyun seems to know something about KaiHo.

December 2012 - Jongin still doesn't know what to do; Junmyeon still looking for Jongin; Sehun looks publicly for Junmyeon.


 

January 2013 - Jongin changes his mind again, looks PUBLICLY for Junmyeon; Sehun is still looking for Junmyeon; Baekhyun still seems to know something; KaiHo's explosion.


 

February 2013 - KaiHo/SuKai evolves; Sehun --> still looking for Junmyeon; Baekhyun/Junmyeon/Jongin are approaching (that's why someone started to ship KaiBaek or SuBaek).


 

March 2013
Junmyeon (and me) still doesn't know what Jongin wants to do with him.

And Sehun keep looking for Junmyeon and is maybe a bit jealous. 

But they seem to be more close than ever, now.


 

* I'm not here to say KaiHo is real, I just reported what I've seen, there are many videos and photos. None of us could know the truth even with a million searches, take my words like a fairy tale to believe or not.

BTW... Jongin. 
It's your own fault. OTL
You should hurry up... Before he goes away. OTL