Eris Boreas Greyrat/Chronology

Volume 2 - Juvenile Period - Home Teacher Chapter
She is introduced as an impulsive and violent character. Initially, Eris didn't have any respect nor did she want to be tutored by Rudeus. Eris had problems with the fact that Rudeus was younger than her, and thus Rudeus had to resort to a different tactic to convince her. Rudeus' plan was to kidnap Eris, and to show her the benefits of knowing magic, reading, and math throughout the kidnapping but due to unforeseen issues the plan derailed. They were kidnapped by men who were planning to sell them off, but Rudeus was able to thwart their plans and save both of them. Seeing Rudeus's magic, Eris was inspired to learn and accept him as her tutor. Later under the guidance of Rudeus she manages to somehow control herself a bit, and she was able to pick up many different skills and improve her magic. Though her magic is no where near Rudeus, her swordsmanship is much better than his.

Volume 3 - Juvenile Period - Adventurer Chapter
She was teleported together with Rudeus to Demon Continent and becomes an adventurer and a member of party Dead End. She trains with Ruijerd to become stronger.

She is seen to often take the vanguard along with Ruijerd in fights with magical creatures, constantly improving herself. At the start, she hardly picks fight because she didn't understand that people were insulting her.

Volume 4 - Juvenile Period - Voyage Chapter
For the first time in her life made friends other than Rudeus in Dorudia Village.

Volume 5 - Juvenile Period - Reunion Chapter
She went to subjugate goblins by herself, but Cliff came along with her. She then compared him to Rudeus and told him he is no good. Later she fought off some assassins and killed a human being for the first time in her life. Later upon returning to the inn where they were staying she found Rudeus in depressed state and comforted him after his fight with his father. Seeing this Eris committed herself to kill Paul Greyrat, however Ruijerd stopped her.

Volume 6 - Juvenile Period - Homecoming Chapter
She fought against Orsted and lost without even landing a single hit. Later she found out that her family died. In her depressed state, she told Rudeus her birthday wish is for him to be her family, after that she lost her virginity to him and then she left to train herself in art of sword. In this Volume her thoughts about Rudeus were revealed as well.

Volume 8 - Youth Period - Special Student Chapter
She appeared briefly in the extra chapter, which described her debut in Holy Land of Swords as well as the introduction of her rival, Nina.

She was seen as 'dangerous' from the start due to her constant bloodlust release and seemingly savage. She is also the reason for Nina no longer being complacent as she poses as a huge threat against her.

Volume 11 - Youth Period - Younger Sister Chapter
Eris appears in the volume's extra chapter, briefly describing her training routines based around the goal of defeating the Dragon God Orsted. She trains everyday swinging and honing her sword and while coming back from training she encounters Auber. Auber stands in the way of Eris and asks her if she could pass a message to Gul Farion, which she ignores and demands that he stands aside. Feeling that Eris is releasing a lot of killing intent similar to one of a wild beast, Auber unsheathes his sword and the two duels. Eris is barely able to keep up and the battle started to heat up to a death battle until Gal Farion intervened. Auber is then introduced and starts trains Eris.

Volume 13 - Youth Period - Labyrinth Chapter
Eris appears in the volume's extra chapter where Reida and her disciple, Isolte, show up as requested by Gal Farion to train Eris. Eris, Nina, and Isolte starts to train together to overcome their weaknesses and learn about the other sword styles. She trains to counter Isolte's Water God Style, which is her weakness as well as Orsted's main sword style.

Volume 14 - Young Man Period - Everyday Chapter
After a duel with the other Sword King Candidates, Eris is named as the new Sword King and was allowed to receive one of the swords from her shishou. Sword God give her the proof of mastery (this was a title that neither the two Sword Emperors, nor Ghyslaine had been given).

Volume 16 - Young Man Period - Human God Chapter
After she receives Rudeus' Letter she immediately traveled to Sharia to meet him. Arriving at his house she met with Aisha, Lilia, Sylphy, Roxy, and Norn. When she learned that Rudeus has already left to fight Orsted, she remembered the reason why she trained in order to stand beside him, and came to aid him. When Eris arrived, she saw Rudeus badly injured and Orsted hurt with his weapon unsheathed. Eris is initially impressed about what Rudeus was able to accomplish simply by himself, and is able to impress even Orsted. Knowing that this is one enemy that they cannot beat, she then urges Roxy and Slyphy to escape with Rudeus. Seeing all of this, Orsted makes Rudeus a deal which Eris initially disproved of, but he still accepted. In the aftermaths of the battle, Eris stays around the house and there was an awkward tension between her and Rudeus. After prodding from Roxy, Eris confronts Rudeus on the current relationship status he has with his other wives and declares that she still loves him. Eris then challenges him to a duel to decide if she could also be loved as well, which Rudeus submits and declares that he still harbored feelings for her and proposes to her, to which she agrees. They consummate their marriage right that night.