I got my 2nd Mabui yesterday from free pull, and my first one in either my 6th, 7th, 8th, or 9th, probably 7th or 8th, pull 10 from kage, I remember getting her in my 2nd rare buildup thing (Example-first 1-5 pull tens are a buildup due to getting a rare at the end, atleast that's how I see it, kinda like seasons, the season finale being once you get a rare.). But Mabui's just a 10% chance every pull 10, it only took my up until my 13th pull 10 to get all of them.

So in all, she's just 1 of ten you can get from kage. Hopefully I got the percentage right.