Lumine uses the medium female model. Both siblings have (blond/blonde) hair, fiery-gold eyes, and pale skin. During their fight with the unknown god, both siblings had yellow wings.
Lumine's hair is paler and chin-length except for two locks of shoulder-length hair framing her face. Lumine also has two light-blue Inteyvat flowers pinned on the right of her head and two pale blue feathers tucked at the left.
Aether and Lumine arrive in Teyvat, yet for some unknown reason the player's chosen sibling does not wake and remained asleep for an unspecified amount of time. The Traveler's sibling eventually manages to wake them up and says that they should leave, with both twins witnessing the destruction of Khaenri'ah. However, an Unknown God, describing herself to be the Sustainer of Heavenly Principles, blocked their way. A fight ensued and resulted in one of the twins getting consumed by red cubes from the Unknown God, and the other trapped in a seal which caused them to lose their powers. Five hundred years later, the Traveler wakes up, separated from their sibling, and stranded. One day they accidentally fish out Paimon from the sea, saving her from drowning.
Paimon would stay with the Traveler and teach them the Teyvat Language: to her amazement, it only took them two months to become a conversational speaker. After learning of how they got stranded on Teyvat at the start of the game, Paimon suggests they get in contact with The Seven, in order to help the Traveler look for their lost sibling. Along the way, the Traveler resonates with a Statue of The Seven, resonating with the Anemo element and allowing them to wield it despite not having a Vision. The Traveler's trip starts at Mondstadt, the City of Freedom, and meet Outrider Amber. Though Amber promises to help the Traveler with looking for their sibling, she mentions that she and the rest of the Knights of Favonius are currently preoccupied with Stormterror terrorizing the city. They help out with the incident, which they find out was orchestrated by the Abyss Order, and learn that the bard Venti is actually Barbatos, one of the Seven, and the Anemo Archon. They also first encounter the Fatui and the Harbinger Signora here, who take advantage of the situation to steal the Gnosis from Venti. They also learn that the Tsaritsa, the Cryo Archon and ruler of Snezhnaya, appears to have unknown motives. Venti apologizes as they know not the God who took their kin away, but suggests they head to Liyue to meet with Morax, the eldest of the Seven and the Geo Archon, who may be able to provide them with answers.
At Liyue, the Traveler and Paimon attempt to meet with Morax at the Rite of Descension, only for him to inexplicably die and are subsequently made a suspect due to being foreigners. They are able to escape with the aid of another Harbinger, Childe, who suggests they meet with the adepti to resolve the issue. He introduces them to Zhongli, a consultant at the Wangsheng Funeral Parlor who can bring them to Morax's Exuvia, or the corpse. Childe's assistance is later revealed to be a ruse as he attempts to steal the Gnosis from the Exuvia but finds that it's already gone. He then breaks the ancient god Osial out of Morax's binds, but with the help of the Liyue Qixing and adepti, they manage to repel the ancient god. Only after resolving the issue do they learn that Zhongli is the actually the Geo Archon, that he was retiring from his position and thus fakeed his death with the help of La Signora, representing the Tsaritsa, of whom he had made a contract with. He hands over his Gnosis for delivery to the Cryo Archon as per their agreement. As the Fatui leave, Zhongli tells the Traveler to head to Inazuma.
While waiting for the chance to do so, they are recalled to Mondstadt where they meet with Dainsleif, who wishes to stop the Abyss Order. Dainsleif warns them against siding with the Archons, mentioning how the gods were the reason why Khaenri'ah was destroyed. During this time, they stop a plot in which the Order was attempting to "mechanise" Osial to do their bidding. Unexpectedly, they manage to run into their sibling, but are shocked to learn that they lead the Order. They attempt to convince their sibling to leave Teyvat with them, but the sibling refuses, mentioning that they still have a war to fight in. The sibling instructs them to continue traveling Teyvat so they can experience the truth first-hand before leaving, with Dainsleif chasing after them. The Traveler attempts to follow but is shut out.
Back in Liyue, the Traveler tries to meet with Zhongli to get answers regarding the truth about what happened in Khaenri'ah, however he says he is bound by contract to not speak of it. With help from the Crux crew, the Traveler is able to bypass the storm and arrives in Inazuma, where they witness the land in chaos due to the Vision Hunt Decree, the Sakoku Decree, and a civil war between the Shogunate and the Resistance. Hearing of their feats in the other nations, Kamisato Ayaka and Thoma attempt to persuade the Traveler to help but are shut down, saying that they are only here to meet with the Electro Archon and nothing else. Ayaka agrees to help them meet with the Shogun but instructs them to first see victims of the Vision Hunt Decree, after which they agree to help with the war. They soon join the Resistance based on Watatsumi Island after meeting the Shogun and nearly being killed by her. In their journey, they meet with the Guuji of the Grand Narukami Shrine Yae Miko, who reveals that the Shogun is actually just a robotic puppet and that Ei, the Archon they are looking for, resides inside it. They soon learn that the chaos in Inazuma was caused by the Fatui and confront Signora, defeating her in a duel before the throne and witnesses her death at the Shogun's hands. The Shogun then tries to cut them down as they leave Tenshukaku, but the timely arrival of the resistance allows the Traveler to confront Ei once more and defeat her with the aspirations of the seized Visions, prompting her to abolish the Vision Hunt Decree. With the chaos resolved, Yae thanks them for their assistance, but mentions that they know nothing about the Traveler's sibling or the Unknown God. She then advises them to make their way to Sumeru next.
While crossing to Sumeru via the Chasm, the Traveler investigates the mysterious area and discovers an Abyss Order plot intending to use a strange water source found in the depths of the cave to restore the hilichurls' minds, learning some of their past from Dainsleif. After this trip, they arrive at Sumeru and are greeted with a vision of a massive Irminsul tree and try to speak with Lesser Lord Kusanali, only to discover that the sages of the Sumeru Akademiya had shut off all physical access to her. The Traveler is roped into a plot by the sages to harvest energy to power a god, upon which they finally meet her while in a dream samsara; with her aid, they are able to break it and free the city's inhabitants. Learning of the full extent of the plot, they manage to find allies to stop the sages, who had been gathering resources to create a new God of Wisdom by empowering Scaramouche. They ultimately defeat him and witness Kusanali remove Greater Lord Rukkhadevata from Irminsul, but as it had not stored data on them, were one of the few who were not affected by the change in data. Ultimately, they chose to keep information about Rukkhadevata a secret to respect her last wish. While talking with Kusanali, they are knocked out by a sound wave by Il Dottore and learn that she had given up both her and Ei's Gnosis for information. Kusanali then suggests they visit Fontaine next to meet with its Archon, Focalors. She also informed them that they were labeled by the Fatui as a "Descender" and that their sibling was not one of them, leaving them wondering if Teyvat had done something to their sibling as they had always been traveling the universe together.
Similarly to the other nations, while waiting for the chance to enter Fontaine, the Traveler meets with Nahida and Scaramouche, the former trying to find information in Irminsul about their sibling and putting the latter into their custody while searching. During the trip, Scaramouche learned the full extent of Dottore's manipulation and willingly erased himself from Irminsul, prompting the Traveler to return to Inazuma to see what changes he had made. They ultimately discover that the changes were minimal, as the events still occurred with different actors and find him in the new iteration as a wanderer. With Kusanali's aid, they restored his memories and the Traveler could rename him.
Later on, the Traveler caught up with Kaeya at Port Ormos before running into Dainsleif yet again, where they investigated Avidya Forest to help jog his memories. During the investigation, Dainsleif went off to investigate the Ley Lines and discovered that the Abyss Order had tampered with them. While he had been investigating, the Traveler encountered a fragment of their sibling's memory, learning how the Abyss Order was founded and their encounter with a "Sinner" that was responsible for Order's foundation.
