Had some more good ideas and a thought.
A while ago I had said if a backlight/ UV light was on the ship and I think Darkrai would unexpectant love it for a hobby she never knew she would like doing, being a Artist/painter. This would seem weird and not like her BUT the art type would fit her so well. She would not use normal paint but the sex fluids from each legend (the color of each of there text is the color it shows as) and the MC cum as her paint that will only show up when in complete DARKNESS and revealed with the black light. Her canvases would be the sheets from the beds of the other legends after making love to the MC since there would be so much cum it would leave a shape of there body on it that the cum did not get under them. Now art is different based on the viewer who sees it so in Darkrai's twisted view she sees the out lines of a body and she adds more splatter to it of diff colors to make it "nightmarish" while others would see a really intense sex session with the MC. Darkrai would even keep the black light in her room as a night light so she can see all her "splatter" in her room on the wall that just makes her drift off to sleep soundly. She could also use the black light to torment the rotem that once they finish cleaning a room she shows them the mess they did not get, they would never get a break and would want to get rid of that light.
Another idea I had is at the end of the game when the MC takes lugia to where he found her she finds something that she had forgotten about. She had ben in that cave for so long that she sat in a spot that conformed to her butt perfectly. Now that she comes back she can now compare how big her ass has gotten since then and boy howdy she got a huge ass now. after having sex she then wants to take ass imprint back with her as a artifact.
A thought I had is if the MC ever wonders why the girls like his cum so much so he asks Maple why and she had already done some research and found out that since he his part Dito his cum auto changes its flavor to be delicious to each of there tastes regardless of their different types or species.