Well, we all know he is one of Kishi's favourite characters, still it was unrealistic how he did it. Cannot copy it. Cannot awakened it since he didn't kill anyone.
Infact uchiha's members are the ones that can, but anyone aside them didnt( maybe because they don't know about MS- yeah), and that's strange, seems Kakashi is the 1st one, but not awakened it like Itachi, Sasuke, Madara, Shisui, etc...
We have story how uchiha member can, but don't have about non-uchicha nor if it's the same way or Kakashi surpassed everyone somehow, and here's the problem- what exactly is so special about him that he did it and the only salution right now is- favourite character, no explanation....