Hmmn... sorta interesting analysis from Natsu Style:
http://blog.livedoor.jp/ustan777/archives/51438439.html
I can't read Japanese, but based on the chinese characters, I think it talked about today's the high index is PROBLY due to FC first press (I assume it's TeamAyu preorder special thingie). They also said avex has done this kinda special preorder gifts recently. They used Kuu's MOON and TABOO as examples. MOON's first day index was like 6 times the second day index, while TABOO was more horrible... 1st day index was about 8 times the second day index.
So basically they predict that Day/GREEN second day index could have a big drop as well..
Hmmmn... I hope what they predicted is wrong... even tho I kinda think their analysis is quite logical..