Where is Activation Code?
 

I bought the game as DVD and after installation it asks for the serial number that I can not find anywhere. Please help me to find it.

It should be stuck in the jewel case or the manual, hope you find it, be aware you are limited to just 3 measly activations after which your game DVD becomes an expensive coaster and you have to buy the game again to play...

Nope its not in the jewel case and I only have a PDF Manual that does not contain any serial number. I bought the game in Turkey during the holiday from a well known computer chain (no chane to be an unillegal copy, paid $35) and now trying to install to my computer in Japan. I bought the previous game here and played without any problem. May it be because of such country difference?

Well, the previous game had none of this 'activation code-online activation required' stuff, so there were no problems.
Places like Turkey are well known for software piracy even if you buy them from good shops that is why I always buy my games online and make sure the games are 'new and sealed' so as to minimize the chance of this happening, although once on eBay I bought an incredibly cheap Russian copy of Batman Arkham Asylum supposedly legitimate from a seller but it turned out to be a bootleg copy, so I lost about $30 dollars, so I feel your pain.
Sadly there is nothing I can do, you can try to order the game from eBay, I am sure there are some that are cheap and post to Japan.
Or get it from here, they post to Japan:
http://www.yesasia.com/global/kings-...0-en/info.html

p.s. Japan, the land of the rising sun, Geisha's and Japanese schoolgirls.
BTW I love those JAV censored movies, they are great!