Looks like the code for Chocolate Cosmos is:

MYNU TAKU EXPO 2016

Someone posted this on the Discord chat.

Thank you! I was just about to ask about it. I tried for Chocolate Cosmos when she came out and didn't get her so I'm really happy now

Thanks a lot. It worked

Thanks a lot! im in need of hit and pierce girls, this code nails it

Thank you really much but... I DONT KNOW WHAT TO DO WITH A 6* AND FOUR 5* TO EVOLVE Q.Q

Thank you, worked like a charm.

Great! Thanks a lot!
That's the kind of gift Nutaku should give in Kanpani Girl from time to time, instead of useless 3*.

Got Cosmos cousins now. Woo. Now I'm out of manyu 😞

thanks man, but i just notice there other campain girls in office where get these codex?

Originally Posted by Unregistered

thanks man, but i just notice there other campain girls in office where get these codex?

Nowhere. They were given out by some mmo site in very limited quantity and long since ran out.
But it is okay, since they are silvers so you will pull them out of normal gacha sooner or later.