The story begins in the town of Wingate, where the A-rank adventurer party "Steely Resolve" celebrates a hard-won victory against a powerful mutant monster. Among them is Mikage, a beautiful, stoic woman with sharp, red eyes, whose formidable presence earns her the nickname "Black Crimson Ogre." To her party's surprise, Mikage announces her departure, citing a "mission" from her homeland. Her kind, muscular male companions, who deeply respect her strength and stoicism, accept her decision, believing she is destined for great things.
However, Mikage's internal monologue reveals her true, vastly different personality: she is a male soul reincarnated into a female body, utterly obsessed with "cute girls." Her "mission" is to form a party with beautiful girls and, ideally, "flirt" with them. She is also cripplingly shy, especially around attractive women, making her goal incredibly difficult. Her cool exterior is a facade to hide her social anxiety and perverted thoughts. She recounts her past: trained in sword fighting by her "sword master" father after reincarnation, she became an A-rank adventurer by taking high-paying jobs, all while secretly yearning for cute girls.
At the Adventurer's Guild, Mikage spots three young women at the beginner quest board. Her "cute girl sensor" goes wild, and she instantly falls in love with the central figure, Riana, a golden-haired girl in a priestess outfit. Riana, a D-rank adventurer, is actually a thief forced into the priestess role by her friends, Karin and Ray, who are also D-rank. Riana, sensing Mikage's intense gaze (a side effect of Mikage's shyness manifesting as a terrifying glare), confronts her. Overwhelmed, Mikage blurts out a comment about Riana's chest size ("C... no, D?"), which Riana misinterprets as a derogatory remark about her D-rank, then flees in embarrassment. Riana and her friends later learn from the receptionist that Mikage is the infamous "Black Crimson Ogre," solidifying Riana's fear and dislike of her.
Riana's party heads to a nearby forest for a simple herb-gathering quest. Deep in the forest, they are attacked by an Ogre, a dangerous B-rank man-eating monster. In a shocking act of betrayal, Karin and Ray abandon Riana, telling her to "die instead" to buy them time to escape. The Ogre seizes the terrified Riana.
Meanwhile, Mikage, regretting her blunder, returns to the guild to apologize to Riana. She overhears two injured adventurers reporting an Ogre in the beginner-friendly forest. Realizing Riana is in danger, Mikage uses her 'Shunpo' (Flash Step) skill to race to the forest. She overhears Karin and Ray's callous conversation, confirming Riana's peril. Mikage finds the Ogre holding an unconscious Riana, its face twisted in sadistic pleasure. Enraged, Mikage swiftly cuts off the Ogre's arm with her katana, "Heshikiri Hasebe," and rescues Riana. The Ogre attacks again, but Mikage, using 'Shunpo' to dodge, unleashes her secret sword technique, 'Kabutowari' (Helmet Splitter), bisecting the Ogre instantly.
Mikage carries the unconscious Riana to an inn, paying the innkeeper, Amelia, a huge sum to care for her. Too shy to reveal herself, Mikage watches Riana from outside. When Riana wakes two days later, she learns she was rescued by an unknown benefactor and vows to thank them, unaware it was the terrifying "Black Crimson Ogre." Mikage, still battling her shyness and fear of being seen as a pervert, decides to become Riana's secret protector.
Returning to the guild, Mikage learns Riana was just there, searching for her friends, and then left with the C-rank party "Silverthorn." Mikage is horrified, knowing "Silverthorn," led by the charismatic "playboy" Telraz, is notorious for manipulating women. Simultaneously, the cunning Telraz had approached Riana, feigning sincerity and claiming Karin and Ray were injured and being treated at his "hideout." Desperate to find her friends, Riana, unaware of the trap, agrees to go with him. Enraged at the threat to her first love, Mikage activates her ultimate, one-time-use sword master skill, 'Shukuteki Kanchi' (Fated Enemy Perception), to track Telraz, declaring him her "fated enemy" and preparing for a confrontation to rescue Riana.