Malty (under adventure name Myne Suphia) was Naofumi's first companion and party members in another world. After noticing that no one joined Naofumi's party, she switched from Motoyasu's party to join Naofumi's party.
At face value, she seemed to have joined Naofumi's party out of kindness but secretly she was doing so to take advantage of Naofumi's good nature.
She used Naofumi as a stepping stone to make him buy equipment for her using his money (by spending more than he could afford), she also stole Naofumi's chainmail and money which she gave to Motoyasu as a present and later accused Naofumi of a heinous crime he never committed - raping her - so she would be able to win Motoyasu over.
Her actions made Naofumi into a dark, cynical, and distrustful person. Naofumi was made out to be a criminal and made the other three Heroes distrust him in the process.
Whenever Myne crosses paths with Naofumi, she will go to great lengths to cause him trouble. She coaxed Motoyasu to force Naofumi into a duel to free Raphtalia, his only trusted companion and source of inflicting damage. She even cheats in the otherwise fair match by interfering with magic.
The duel was announced as Motoyasu's "victory" after Myne's interference. It was later discovered that Myne was actually the First Princess of Melromarc and that her real name was Malty.
While rewarding the Heroes, she persuades her father to reduce Naofumi's reward for freeing his slave but didn't have her way. When Motoyasu was named as the lord of the newly-rebuilt Riyute Village, she was in his stead, levy heavy taxation on the Wave-affected village. After receiving orders from higher authority to back down, she challenged the Shield Hero for a Dragon Race with Motoyasu, for the lordship of the village.
She also cheats by having her guards cast magic to slow down Naofumi and boost Motoyasu in their mounted race, but even through these dishonest tactics, Naofumi and Filo's determination granted them victory. Even though Malty denies this and has supporters agreeing with her, her antics have been called out by others outside her influence, mainly her mother's Shadows.
When her younger sister Melty's life was under threat, Malty went along with the Heroes and tried to "rescue" her. However, it soon became clear that she was actually attempting to murder Melty, so she would inherit the throne and frame Naofumi for Melty's death. Ren and Itsuki both noticed Malty's suspicious behavior, while Motoyasu once again remained completely oblivious.
She continuously hunts down Melty and Naofumi in an obsessive way, even to the point of burning down an entire forest to find them. Finally, when the Pope revealed the conspiracy, she turned pale and started blabbering. Naofumi, after a very hard fight, defeated and destroyed the Pope.
The Queen exposed all of Malty's crimes, stripped her of royalty and, as an extra punishment on Naofumi's suggestion, renamed her "Bitch" for her false rape claims. Alternative acceptable names by royal decree include "Whore" and "Slut." She has never repented for her misdeeds and always tries to find ways to hurt or eliminate Naofumi, as she believes her downfall and subsequent misfortunes were entirely his faults.
After losing her status and name, Queen Melromarc ordered Malty to remain as a companion with the Spear Hero Motoyasu. She joined him during the Cal Mira Archipelago bonus event and was present during the fourth wave although she did very little to help.
Eventually, Queen Melromarc organized training sessions for the heroes with experts around the world. However, Motoyasu, along with Malty, decided to leave the country to skip out on training. Before they could, they were barred from leaving the country due to the excessive debt that Malty had given Melromarc when she was in control. As an alternative to training, the Queen gave them an option to investigate a mysterious catastrophe occurring around the world. They used this as an excuse to abandon Melromarc to do their own wishes.
During the Spirit Tortoise Catastrophe, Malty's slave crest had lost some of its functionality due to the Guardian Beast. As a result, she, along with Motoyasu's other companions, decided to abandon the Spear Hero as soon as it became clear that he was useless against the monster. After being saved by Naofumi, Motoyasu had sunk into a deep depression by his companions betrayal.
While Ren is grieving the death of his companions from the same catastrophe, Malty and Lesty approach him. They renounce Motoyasu and slandered him by complaining that he had abused them. They also blamed Naofumi for controlling the Spirit Tortoise that killed Ren's companions. Under Malty's manipulation, Ren trains Mald how to use a sword. The next morning, Ren finds that everything but his sword had been stolen from him. As a result, Ren becomes enraged and unlocked two curse series weapons during his rampage.
Soon after Malty and her companions had taken advantage of Ren, they then move on to Itsuki. They lied to Itsuki about evil deeds from the other heroes and then use the Bow Hero's sense of justice to manipulate him. They convinced Itsuki to fight in the coliseum to raise money to "save" people while they bought food, gambling, and other luxuries in Itsuki's name. It is also through them that Itsuki unlocked his curse series weapon. By the time Naofumi and his party rescued Itsuki from his own rampage, Malty and her companions had already left with an insulting note and massive debt.
Unknowingly to the heroes, Malty had started to manipulate Takt - a vanguard of the waves with the power to steal Vassal Weapons and Legendary Weapons. When the heroes go on a diplomatic mission to Faubrey to negotiate with King Faubrey, they find Takt in his place who sprung his ambush. In the ambush which Malty had instigated, her mother (Queen Melromarc) was killed and Naofumi was greatly injured. With her mother's blood she was able to release the slave crest that had been on her since her trial in Melromarc. Then, Takt started his campaign to take over the world. When he was defeated, Malty was able to slip away.
Malty was next seen in Glass' World, manipulating Miyaji alongside S'yne's sister. As revealed in Volume 18, in between Takt and Miyaji, Malty and her companions had been travelling between different worlds. They eventually landed in the same world as the S'yne's Sister's leader who almost had their last Legendary Hero killed by a group a terrorists. Malty prevented the hero's death (and thus prevented that world from being destroyed). As a reward, they were able to join the organization behind the waves and put under S'yne's Sister's charge..
Miyaji, another vanguard of the wave, was then manipulated by Malty. Together, they were able to kidnap Kizuna (the final hero of Glass' world). When Naofumi and the other heroes stormed Miyaji's compounds, they fought Miyaji, Mald and Malty. Naofumi was able to reflect one of Malty's powered-up spells back at her which caused severe damage. However, S'yne's sister was able to teleport Mald and Malty away to safety.