Melty was sent to Melromarc by her mother, for two reasons, one for her father wanted to see her, second was for Melty to fix the relation between her father and the Shield hero. During her return, she lost her path and got tangled up with a few wild Filolials. She was escorted to Castle town by Naofumi without knowing who the other person was. During their travel, she befriends Filo. She made few attempts to persuade the Shield Hero to talk to her father but failed. After the third wave, Naofumi emerged victoriously and was taken to the castle where he openly mocked and threatened the king. Melty demanded Naofumi to have a serious discussion with her father but was ignored. Naofumi was preparing to leave the country for a class-up. Melty chased him with her demand for an apology and reasonable talks with her father.
Melty became the target of an assassination plot by the Cult and was taken under the protection of the shield hero. Her assassination attempt was pinned on Naofumi and a bounty was placed on his head for a hefty amount. She deduced her sister involved in it, for the throne. Left with a few options, Naofumi decided to go to the demi-humans nation, as the king of Melromarc was biased against the shield hero and their previous encounter may add to their sourness. Naofumi plans to take Melty with him and negotiate after the queens' arrival, in which Melty reluctantly agrees to their proposal.
She came to defend Naofumi of false charges to the heroes, but she was accused to be the victim of brainwashing by the shield hero. Both the soldier and heroes party including Malty's group made many obvious attempts on Melty's life. but was saved by Naofumi and his party. They were able to escape with the aid of her personal shadow. Following the Shadow's advice, Naofumi changed his destination from Siltvelt to Faubley, in order to meet the Queen.
They were still chased by Motoyasu and ended up in Van Reichnott's place. One thing after another leads her into the hands of Idol Rabier. Naofumi ended up fighting the noble and killing him. Raphtalia recollects her painful experience in Idol's basement and the death of her best friend. They were also able to find another Raphtalia's friend, Keel and rescued her.
Melty thought she understood how strained the Human and Demi-human relations were. But was shocked to see the horrors done to the demi-humans in her own country with her own eyes. Idol, in his dying breath, released the sealed monster in the middle of the kingdom to kill Naofumi and his comrades. The Shield Hero dragged the monster to the outskirts of the nearby town and fought it with no success. Finally, Fitoria shows up and saved the day.
Melty promised to work hard for both the demi-humans and humans to have a peaceful life in her country. After Malty's punishment was put in effect, she took the position of next in line to become Queen. Her mother offers her hand in marriage to Naofumi as part of a political marriage to which she just blushes over.
By the time Naofumi and his party had returned from Glass' World, several weeks had passed by. As his reward for the Spirit Tortoise incident, he asks for the Seaetto territory. Upon arriving there he finds that Eclair had made some rebuilding progress - however this was mostly thanks to Melty's efforts.
As Melty was playing with Filo, suddenly Filo fell ill. It was revealed to be the Demon Dragon Emperor siphoning Filo's levels for himself. Melty then joined Naofumi's forces to take down the Demon Dragon Emperor before it destroyed Filo. Partially thanks to her impressive magical skills they were able to defeat the Demon Dragon. However, it was also revealed that Melty's levels were relatively low so Naofumi forced her to go power-leveling with Filo.
During power-leveling with Filo, Melty reached level 40 and the two met Fitoria. Through the two of them Fitoria asks Naofumi to take care of a filolial issue and places several blessings on Filo and Melty as advance payment.
Since the reconstruction efforts in the Seaetto territory had begun months ago, Melty had assumed unofficial responsibility since Eclair ended up being a terrible governor. Due to her efforts, Naofumi demotes Eclair and places Melty officially in charge on his behalf.
In an ambush by Takt, Queen Mirellia was dealt a mortal blow. With Melty being first in line for the throne, she was declared the new Queen Melromarc. After briefly grieving, she quickly restored her resolved and started leading Melromarc in the battle against Takt. Combined with her newly revived father's wisdom, they were able to successfully defeat Takt's forces.
With the immediate concern of Faubrey's invading forces resolved, the official coronation of Melty was conducted. As the popular princess, she eagerly welcomed by the Melromarc public and representatives from other nations. After the official ceremony, Naofumi teased Melty about her position and high responsibility. In retaliation, Melty bestowed Naofumi with the title of archduke as a royal edict. However, immediately as soon as it was done, Aultcray happily reminded that two that the archduke typically marries the queen and so the two may be considered politically engaged. The two consider that with repulsion but there was no easy way to undo the royal edict. And so, Naofumi remained as archduke.
As Naofumi and his party returned from Glass' World for the second time, they find that Melty has been doing relatively well as queen. However, Melty complains of being worn out by the many meetings and other official business as well as the threat of being assassinated. Thankfully, she has her father as an advisor to provide a lot of help.
However, as she is providing an update to Naofumi in his village, the entire village (including Melty and her shadow) are sent back in time. With Melty's wide knowledge of history, they are able to figure out when they are. She also acts as a political representative which helps Naofumi and his village build positive relations with Mamoru and Siltran.