Leo had met Alice in her previous life on different occasions. Having the title, 'last man standing' and a lot of coincidence that allowed her to survive despite others who were far more powerful than her dying, made it evident that her title was in effect.
She would be the last man standing at the end, so he approached her.
Titles weren't given to specific Awakeneds on Leo's directive. The system seemed to see a person's deep potential and read their fate when they get attached to them.
So, that title was basically their fate whether they liked it or not.
The first time Leo approached Alice was when she lost Devon.
On that day, when she was to be a member of the Snow Guild, there was an ambush. A monster ambush. It was apparently being led by someone, and his guess was the demons, but they did not come out of the shadows.