Each series can be read independently of each other.

• Earth Girls
  This story takes place thousands of years ago, in an era before modern civilizations. Our protagonist Sakina decides to venture forth to find the rumored Smoke Mountain, a village ran by a female chieftain named Kidaha. During her adventure she becomes caught in a fierce storm with a mysterious girl.  (From: Yuri-ism)
  Amazon.co.jp

• Earth Girls Tumugi
  In this prehistoric world, Yuuri is a young girl troubled with insecurities because of a past injury. One day, a woman named Kidaha visits the village to barter and encourages Yuuri. Rumour says that this woman comes from a village of only women. Marriages, too, are only between women. If she moves there, will Yuuri be able to lose her fear and find a fitting home… and wife?
  Amazon.co.jp

• Earth Girls Kazitu
  Our protaganist, Katra, is enticed to leave her home by a womanizer woman she meets while picking fruit. With promises of yummy food, expect Katra to be happy and well-fed in her new village.