The FL is same, their characters are almost similar. Independent, free-willed, strong, quick witted and supporting their partners to the very end.

The FLs are smart and always looking for opportunities to turn tables. Both, kind of showcase their change of ideals over time spent with people.

Both start with a innocent and naive lead (FL in SF6 and ML in SF4), and they have some mysterious power, which resonates with the other lead. Both belong to the Sword and Fairy series but the stories are not connected, so feel free to watch them