If you're looking for manga similar to Maple Story, you might like these titles.
In the warmongering nation of Erebonia lies Thors Military Academy, a premier institution attended by both the nobility and the common folk alike. Rean Schwarzer, a new first year, learns that he, along with eight students of wildly different backgrounds, have been selected for the experimental Class VII - a new class in which the established social hierarchies are not recognized. But tensions are high in the Empire, and Rean and his new classmates may soon find themselves embroiled in conflicts far beyond those of the classroom.
In the center of the land lies the human kingdom of Radiata and surrounding it are the lands of fairies, elves and goblins. The relationships between the two species were never good but things got worse after the attack of the dragons. Today is the Knighthood entrance exam for Ridley Timberlake and she has been training for this moment her entire life. Winning the tournament today means she will be initiated into the knighthood. Her first round is against a boy her age named Jack Lassel and she defeats him with ease. She fights her way to the finals where she becomes the champion and a knight only to find out that Jack, who is the son of the legendary dragon slayer, was also inducted.
The year is 200X. Jin, Akira and Lena are three child hood friends who like mysterious things. One day in the library, along with the mysterious transfer student Ami, they find the "Akuma Compendium". They chanted an incantation in the book and, to their surprise, devils appeared. Ami then told Jin and Akira that they are the Devil Children that will decide the fate of the world. She hands them their Devil Risers. The group then pass through the "Door of Time" to the land of Valhalla where they fight an evil ruler known as Imperius who plans on conquering all of the world. The Nakama of Jin is Rand, a Sol Lion, and Akira's is Gale, a Hylon.