Mjur Farmenas/Chronology

Demon Lord Attack Arc
Mjurran was assigned by Clayman to secretly investigate the Jura Tempest Federation, but she could not get too close as it might draw the attention of Demon Lord Milim Nava, who had spotted her, so she chose to observe from afar for the time being.

Demon Lord Awakening Arc
Since Mjurran could tell Clayman's interest in herself was dwindling, and since Milim ended up leaving, she decided on a more hands-on approach of getting into the Champion Youm's entourage. To do that, she went to the Kingdom of Falmuth where Youm comes from and usually does his work and gained an adventurer license there. She then requested to join Youm's party but was instead looked down upon. After defeating Youm, Rommel, and Jagi, she was welcomed into their party and became their advisor.

After joining Youm's group, she became responsible for giving tactical advice to the party and providing in-the-field guidance on working together to fend off monsters and magical attacks. She openly revealed that she is a Wizard and gave her teachings to Rommel, Jagi, and everyone else in the party that was at least somewhat familiar with magic.

As a military adviser, she also had the vital role of casting the deciding vote on the party's actions which, however, also increased her responsibilities and work further.

Days passed on as Mjurran firmed up her position on Youm's team and taking part in their work through which Mjurran continuously felt more pleasant about her situation.

Later, the group headed back to Tempest.

Back in Tempest, Grucius had underestimated her and was defeated making him fall in love for her. When Gobta saw this, he had asked her to help him and Youm in defeating Hakurou. Mjurran reluctantly accepted her participation in the mock battle, but Hakurou ended up defeating all of them on his own.

Time passed, and Mjurran ended up falling in love with Youm, but Clayman anticipated that and used her newfound feelings to blackmail Mjurran into taking up "one last mission" for him, which is the deployment of an Anti-Magic Area over the whole of Rimuru City at a predetermined moment.

In her situation, Mjurran using that Great Magic that blocks the use of magic, would have the effect of immediately exposing herself as a Majin and it would make her a target of resentment for Tempest, while also sealing up her own means to defend herself. Clayman hoped that this would provoke them into killing Mjurran, giving him a Casus Belli to later excuse military action against Tempest, in case Tempest ends up winning the confrontation with Falmuth.

Mjurran, preparing to cast the Anti-Magic Area, turned into her Majin form, but before she could follow Clayman's order, Grucius and Youm caught her red-handed. She is asked to stop by both, but due to Youm not detesting or fearing her due to her appearance as a Majin and instead him even claiming that he loves her, it emboldened her resolve to sacrifice herself to not give Clayman any reason to get rid of Youm and so she decided to follow Clayman's order to the end.

Afterwards, Rimuru, who had just returned, ordered Mjurran, alongside Youm and Grucius, to be put into house arrest.

Rimuru, a short while later, came to her place of detainment together with Benimaru to interrogate her. Mjurran revealed everything, as she did as ordered by Clayman and no longer cared about her own life. After Rimuru decided he heard enough, he proclaimed that Mjurran's punishment would be her death. Youm and Grucius tried to interfere but could not hope to put up a resistance against Rimuru and Benimaru. Before her punishment was enacted, she told Youm that she also loves him and that he "shouldn't be tricked by another woman like her in the future."

Following that, Rimuru approached Mjurran and then used Gluttony to phase through her body and clothes to directly crush her "Marionette Heart," replacing it with a similar "Pseudo Heart." Rimuru then explained that Clayman's Marionette Heart was like a wiretapping device that allowed Clayman to listen in on their conversation and that the Pseudo Heart does not have a "paired" counterpart, nor the wiretap function, so Mjurran had essentially become free without losing the benefit of eternal youth. Mjurran then accepted Youm's declaration of love as she "didn't mind being tied down for the short duration of a human life."

After Rimuru explained his plans of having Youm take over control over the Kingdom of Falmuth, Mjurran decided to help Youm become a king and guide the nation as to never oppose Rimuru ever again.