Marriage isn't considered progression?If you mean progressing romance there really are none. The only a few characters I believe have a hidden relationship score are Atani, Zo, Quin, and Valencia. Atani's can't go down, Zo has nothing to hers other than her training getting a bit more frisky, don't know how in-depth Quin's will be, and I can't tell you about Valencia. Most other character is just do a handful of quests for them and then you'll have them.
Kiyoko probably is the best romance option because while there is no progression after Kinu, you can, at-least, do things with her.