The protagonist of season one consist of Ryu, martial artist practioneer and his friend Nash a boy who wields a ultimate sword of power. Along with their allies Mario and Luigi they journey the world of Fictopia looking to save it from evil.
Ryu is the lead character from the Street Fighter series and a main character in the Ultimate Adventures season one storyline. In Ultimate Adventures he is potrayed as a brave martial artist who determined to save the world from the forces of his evil rival, Akuma. His goal is to find and locate the Five Heavenly Arms and destroy them to restore peace to Fictopia.
Nash is a sixteen-year-old boy and original character to the Ultimate Adventures universe. Nash is shown to be highly curious as he is prompted to search a mysterious cave outside of his town. Upon traveling the cave he comes across the Heavenly Sword, one of the Five Heavenly Weapons. Nash continues to wield the Heavenly Sword, using it to fight against evil alongside Ryu.
Mario is an italian plumber who travels around Fictopia looking for work with his younger brother, Luigi. Hoping to find Princess Peach, who was kidnapped by Bowser and his Koopa Troop, Mario and his brother Luigi join forces with Ryu and Nash and help them on their quest.
Luigi is an italian plumber and younger brother to Mario. Mario and Luigi come across Nash and Ryu on their travels and decide to join forces with the two hoping to find their friend Princess Peach. Luigi poses as the series' primary comic relief character due to his tendency to get into trouble.
Akuma is the main antagonist of the series and enemy of Ryu. Akuma's goal is to become the strongest fighter and take over Fictopia, to do so he must wield the Five Heavenly Arms. Akuma is known to be a naturally strong being, Ryu claims that if he were to gain possession of the Five Heavenly Arms he would become unstoppable.
Bowser appears as the main subordinate to Akuma and enemy to Mario and Luigi. Before the beginning of the series he has his Koopa Troop capture Princess Prince so he can claim the Mushroom Kingdom as his. Bowser is portrayed as an absolute idiot in Ultimate Adventures and primarily orders the Koopa Troop to do whatever Akuma orders.
The Koopa Troop Bowser's minions that he normally uses to carry out the orders of Akuma. They do most of the dirty work as they pillage and raid the towns of Fictopia and do most of the searching for the Five Heavenly Arms. The Koopa Troop itself in size is a large scale army and primarily consists of Koopa Troopas.
The Mushroom Kingdom is a nation located to the far east of Fictopia. Mario and Luigi are from this kingdom and it is ruled by the peaceful Princess Peach. The Mushroom Kingdom and it's inhabitants later become important allies to Ryu and Nash.
Princess Peach is the leader of the Mushroom Kingdom and friend to Mario and Luigi. Before the beginning of the series she was captured by Bowser and his Koopa Troop as an effort to gain control over the Mushroom Kingdom. She later becomes an important ally to the protagonist often offering them supplies and such.
Toad is the anthromorphic mushroom servant to Princess Peach that resides in the Mushroom. In most cases he is the company of Peach and was even with her when she was captured by Bowser and his Koopa Troop.
Sonic the Hedgehog is an ally of Ryu and his friends. At first he attacked Nash attempting to take his Heavenly Sword but later decided to befriend the group after Ryu explained the situation. Although Sonic does not travel with the group he is a promient ally as he helps whenever he can.