Crusader Kings III

Easily done as Mogadishu in 1066. Make a custom ruler with high martial/prowess and of Jewish Faith. You are a medium fish in a small pond and can easily get the necessary land with your god ruler-commander for a kingdom in a couple years. Do not waste any of your prestige or money early on, as you will need money to form titles and prestige to diverge your culture.

Begin by working your way to the right. Almost all of the nations next to you are independent counts and will easily fall to your holy wars. Don't worry about losing piety or devotion, you will never need those. Conquer just enough to form the duchy of Mogasihu, and then conquer enough to form the duchy of Hafun or the duchy of West Ajuraan . Both cost a bit of money that you don't earn much of, so investing in stewardship might be worth it. After that you should have enough land to form the Kingdom of Ajuraan, and will just need to wait on money to form it.

Then simply get enough prestige to change an aspect of your culture and diverge it. (which if you haven't spent any up to this point, combined with the prestige from creating titles, should be easy).

Had this done in about 30 minutes, if that.