Summary
Kushina died during the Sealing of Kurama. She figured that she would be in the pure lands and wait for her son as she knew that Minato would never be allowed in the pure-lands for using the Reapr Death Seal. Only Kushina didn't go to the Pure Lands. She was stuck in the land of Mortals tethered to Naruto, never allowed to be more then five miles from him, protecting him.