The story begins with a vivid dream experienced by the protagonist, Yuri. He witnesses a scene from the future where his close friend, Theo, announces his impending marriage. This declaration, however, is revealed to be a death flag, leading to Theo's demise in a brutal war. Yuri, as Theo's protector, sacrifices himself to save Theo, lamenting his own fate and the heavy cost of their victory. Theo, a hero destined for greatness, is devastated by Yuri's death, desperately trying to heal him with magic but to no avail. Yuri's last words are a plea for Theo to look after someone, and he dies with a hopeful gaze.
Yuri awakens from this realistic dream, realizing he has been reincarnated into the world of his favorite RPG, "Seiso no Astrea." He is now Yuri, a character from the game, and his friend is Theo, the protagonist. The dream depicted them as older, hinting at a future he now has knowledge of. Yuri recalls his past life as a salaryman in Japan who died from overwork, only to be reborn in this fantasy world. He remembers that in the game, Yuri was Theo's friend but eventually turned to darkness, only to reconcile with Theo before the final battle. A crucial detail is Yuri's impending death flag related to marriage.
Determined to change his fate, Yuri decides to alter the game's narrative. His goals are twofold: avoid the marriage death flag by not forming romantic relationships and gain enough power to survive the upcoming "Starfall War." He leaves his home and heads to the Adventurer's Guild, where he encounters Theo and Sophia, the main heroine. Instead of the expected confrontation where Yuri would expel Theo from their party due to jealousy, Yuri preemptively announces his departure. He claims to be a hindrance due to his dark attribute skills, which attract monsters and could endanger them. Theo and Sophia are shocked and saddened, but Yuri remains resolute, believing this separation will allow Theo to grow and avoid tragedy. He promises to meet them again as powerful adventurers.
Yuri then embarks on a journey to the Kingdom of Levallis, aiming to gather information and increase his strength. Along the way, he encounters a Griffin attacking a carriage. He intervenes and, using his skills and magic, swiftly defeats the creature. He discovers the woman in danger is Saint Ria, a heroine from the game. Ria, whose passive skill "Affection" makes her beloved by most beings, is unaffected by Yuri's "Evil" skill, which instills fear. They form an alliance, with Yuri agreeing to be her bodyguard, as Ria suspects she is being stalked. Ria invites Yuri to stay at her large mansion, which he accepts, though he remains wary of forming any romantic entanglements that could trigger his death flag.
During his stay, Yuri discovers Ria's hidden, less-than-saintly side, including her use of a pipe-like flower for stress relief and her cynical view on the role of a saint. Despite this, he finds her more relatable and agrees to her request to move into a room closer to hers. He also begins to teach her combat skills, revealing her surprising strength and potential. Yuri continues to train, aiming to master his abilities and prevent the looming war. He also learns about Ria's past as an orphan and her desire for a family.
As Yuri trains and prepares for the future, he encounters a C-rank adventurer named Baldo, who recognizes Yuri's unique abilities and offers guidance. Yuri also begins to suspect that the Griffin attack on Ria might have been orchestrated. He continues to hone his skills, particularly his control over his "Evil" skill, which he learns to suppress. He also witnesses Ria's growing dependence on him and her desire for a normal life, including the simple act of saying "goodbye" and "hello."
The narrative progresses with Yuri and Ria developing a comfortable, almost familial relationship. Yuri teaches Ria about cooking and combat, and Ria expresses her desire for a husband and a family. Their interactions are tinged with Yuri's awareness of his own death flag and the need to maintain distance, while Ria seems to be developing deeper feelings for him. The story also hints at a looming darkness and the possibility of a conspiracy involving the Griffin attack. Yuri's actions are driven by his knowledge of the future and his determination to survive and prevent the war, while Ria finds solace and happiness in his presence. The chapters conclude with Yuri preparing for his next steps, including venturing into a dungeon, while the underlying threats and mysteries of this world continue to unfold.
