Zoku Kinsei Tokkyuu Ryuuketsu no Musume

Sakura grew up on Inuhebi Island, a remote island inhabited only by women. One day, when she turned 15, two mysterious men landed on the island. When one of the men spotted Sakura, he said with a big smile, "We've come to pick you up, Sakura." Introducing themselves as Mitsuki and Sunaetsu, they were associates of Sakura's father and seemed to know about her past, something that even Sakura herself didn't know. Sakura decided to leave the island with them to see a world she had never seen before, but...

(Source: Shinshokan, translated)