Hey there got a question, a friend of mine started on dmm a few weeks before me and he has this unit

http://seesaawiki.jp/aigis/d/%b7%f5%...c6%a5%a3%a5%a2

I read that for sapphire units you need the serial which you get by geting the novels and stuff like that.
But he didnt spend money for it, so was there an event I missed or is there a way to get her?

I mean her skill looks great and kills very fast, hope I can get her somehow