Risty was engaged to Leon and it was known that they loved each other. Risty was depressed when she found that Leon died while protecting Akastuki from the Demon Lord.
At first, Risty seem to dislike Akatsuki and end up hating him for the cost of her lover, Leon. However, after Akastuki came back stronger and braver, Risty developed feelings for the rogue hero, but tend to get annoyed at him and was upset when he left her for the Human world (not knowing his promise to the Demon Lord.) Risty became a part of Akatsuki's Harem after she found out the truth about Leon, and she returned with him back to his Homeworld in volume 4.
This does not happen until much happens in the story because Risty and the other leaders of Alazard declare Akatsuki a enemy after he sided with the Demon tribe, and he had to fight Risty, and Miu had to do it but evidence was found that Akatsuki was right about the Demon tribe because someone wanted them to be destroyed, and the leaders were bigoted and biased against them.