Answer One: I believe real karate is that traditional/classical form practiced on Okinawa. I am not speaking of the sport aspects or the school driven version but the combative version once referred to as "ti or toudi." If the system or branch practiced in the west, here in the USA, etc., is derived from the "ti or toudi" versions which can be referred to as shuri, tomari or naha based then it is real karate. This is a loaded question and answer because to be traditional/classical fighting system means removing all the layers to find all of it. Most of what is practiced in the west today is nor real karate - my opinion.
Question Two: What makes it real?
Answer Two: Read answer one.
Question Three: What can we do to keep it from not being real?
Answer Three: By practicing it as it was meant to be practiced. Not be remaining in a dogmatic remain unchanged and identical to what Tatsuo Sensei taught except to keep the fundamental practice the same for future generations but to add to that foundation to crate a unique and individual perspective/context for your practice and no one else's.
This type of discussion goes on forever and I believe that these answer are not all encompassing but rather the type that work like a zen koan where you contemplate on the idea's and then allow the intuition of your mind to bring out more .... much more .... and if you can do that successfully then you don't need to ask these questions unless you want to inspire the younglings in the dojo :-)