Onimushi - Vol. 1 Ch. 5 - Omens

[MangaDex]

 

[zawarudo]

The real Tana drifted off and got rescued by mainlanders, conceived Maname with some mainlander dude, and circumstances happened that led to Maname escaping to sea only to drift back to the island. When she said "although..." in chapter 1 it's possible she was about to say "...you look like my mom".