I think I've done all the steps for it but is yet to show up on the quest board, I want to get the weeding quest for Shanna and Naomi and saw that I need to start this quest for it
(I've gotten solo and onsen scenes with Shanna and Naomi)
For the bounty to appear on the Aldlyn city board, you require the wedding system to be unlocked, the solo CG scenes with Shanna and Naomi, as well as their secret onsen scene. If you have the solo and onsen scenes, that it's probably the wedding system you're missing.