If you're looking for manga similar to The Legend of Maian, you might like these titles. All recommendations are made by Anime-Planet users like you!
In both series a powerful and evil woman\girl finds herself a new toy in the form of a somewhat weak boy. Even though she actually loves him (or more likely that's her twisted way of showing affection), she just can't help but toy with him and tease him mercilessly. In both series the female lead is on a quest to take over the world (which also includes destroying it in Shihou Sekai no Ou). If you liked one of those two series, odds are, you'll like the other one as well.
In both manga there was this big battle between and an end boss and a hero (or heroes in case of Lost Seven). Years later, one of the two meets up a descendant of the other, they start traveling together and grow feelings for each other. It's just that, in case of Legend of Maian we have the descendant of the hero traveling with the end boss and in Lost Seven we have the descendant of the end boss traveling with the hero. If you liked one of those two series, the other one might be worth a shot.