The narrative picks up with Claire, a 417-year-old elf, meeting a young human named Matthew or Marsh. Claire, immune to poison and thus unaffected by alcohol, enjoys listening to adventurers' tales, finding her long elven life in her village monotonous. She views human men's invitations to drink as attempts to get her drunk and take advantage, but her immunity always thwarts them. Her true enjoyment comes from the stories they tell.
Marsh, the human, reveals a secret: he is an otherworldly reincarnator. He explains that he died in an accident with his best friend in his previous world, Japan, and was reborn in this fantasy world with his memories intact. His primary goal is to find his lost friend. Claire is intrigued, as the concept of reincarnation and the mention of his friend's name, Hiiragi Kazuya, stir a forgotten memory within her. She reveals her own past life as Hidaka Mik, and her friend's name, confirming their shared past. Kazuya, shocked and overjoyed, realizes Claire is his long-lost friend, Mik, now an elf. Claire, who had reincarnated 400 years prior and spent centuries searching for Kazuya, had forgotten him until this reunion. She expresses her frustration at the long wait but is happy to have found him, resolving to spend his remaining human lifespan with him.
Kazuya, now Marsh, is surprised by Claire's transformation into an elf. They discuss their shared past and Claire's frustration with the 400-year wait. Marsh admits he was initially drawn to Claire's beauty, but their reunion as friends overrides any romantic intentions. Claire, having forgotten her past for a long time, is now determined to stay with Marsh. They agree to travel together, with Claire offering to accompany him until his death, seeing it as a way to alleviate her own boredom.
The next morning, Marsh wakes up to find Claire naked beside him. Claire explains she always sleeps naked and had carried him back to his room after he got drunk. This incident, along with Claire's habit of sleeping naked, creates awkwardness and a growing distance between them. Claire eventually starts wearing clothes to sleep, which Marsh interprets as a rejection, leading him to stop waking her up. Their interactions become strained, and they begin to drift apart, even during quests.
During a quest to defeat Breath Spiders, Claire's distraction causes her to be caught in a spider's web. Marsh, despite their strained relationship, rushes to her rescue, demonstrating his strength and concern. This event prompts Marsh to confess his feelings for Claire, admitting he has fallen in love with her as a woman, not just a friend. He explains his desire to bridge the gap that has formed between them and to awaken her dormant elven romantic feelings. Claire, though initially hesitant and still seeing him as a friend, acknowledges her own feelings of affection and decides to accept his advances, agreeing to share a bed and work towards a deeper relationship.
Their relationship progresses, and they become a formidable duo, quickly rising through the adventurer ranks. Marsh is revealed to have "Hero Aptitude," a rare trait that enhances his abilities and allows him to take on higher-ranked quests. He is officially recognized as a Hero and aims to defeat the Demon Lord. Claire, a powerful mage, becomes his indispensable partner. They face challenges, including a difficult dragon-slaying quest where Marsh's sword breaks, but they overcome it together.
Marsh's desire for a two-person party to defeat the Demon Lord stems from his belief that any other man would be drawn to Claire's beauty, and that he himself can no longer see other women as anything but friends. Claire, though initially finding his reasoning flawed, eventually agrees to their two-person party, realizing her own growing feelings for him and her desire to be by his side. They continue their adventures, with Marsh actively pursuing Claire and Claire slowly reciprocating his affection. The narrative concludes with them preparing for a dragon-slaying quest, solidifying their partnership and hinting at their future endeavors.