Sagiri Izumi is a petite and youthful girl with fair porcelain skin and long silver hair. Her hair is styled with two small pink ribbons at the sides of her head, additional pink ribbons at the ends of her hair, and a large pink ribbon tied at the back. She has large, expressive blue eyes that enhance her delicate appearance.

Her typical attire consists of pink pajamas, often paired with a dark green hoodie worn over them. She also wears pink slippers adorned with bows, matching the soft and cute aesthetic of her outfit.

Sagiri is usually seen with a calm or neutral expression, though she occasionally displays embarrassment or smiles, particularly during moments of emotional connection with those around her.

Sagiri Izumi is portrayed as a reclusive hikikomori who has difficulty interacting with others. She is shy, soft-spoken, and easily embarrassed, often choosing to communicate with others especially her brother Masamune through a speaker rather than face-to-face. Despite her reserved nature, Sagiri becomes more animated and expressive during her live illustration streams, though she is careful to conceal her identity by masking her voice and hiding her face.

Initially distant and cold toward Masamune, Sagiri gradually begins to open up to him as they spend more time together. She is shown to be neat and organized, keeping her personal space clean and well-maintained. However, she can be quick-tempered and is prone to jealousy, especially when other girls get close to her brother. Though she often hides her emotions, her actions reveal a possessive and protective side, and she occasionally throws tantrums when feeling neglected or frustrated.

Sagiri is passionate about drawing and takes great pride in her work as an illustrator, even though she is reluctant to associate herself with the pseudonym “Eromanga Sensei” due to its suggestive nature. Despite this, she admits to enjoying the process of drawing erotic images. Her stubbornness is also evident when Masamune forgets to bring her food, she refuses to leave her room out of principle, viewing it as a matter of pride.

One of Sagiri’s heartfelt dreams is to one day watch an anime adaptation of their work together with Masamune, reflecting her desire to connect with him not just as family, but as creative partners.

Sagiri Izumi was first introduced through a flashback, where Masamune recalls meeting her for the first time. During that moment, she shyly greeted him by hiding behind her mother’s back and saying, “Hello, Big Brother.” However, following the deaths of their parents, their relationship became strained. Struggling to cope with the trauma and loss, Sagiri shut herself away in her room and became a hikikomori.

Her reclusive lifestyle remained unchanged until an incident involving one of her livestreams. Sagiri, who had forgotten to turn off her camera before changing, was interrupted by Masamune, who banged on her door in panic to warn her. As he leaned against her door to catch his breath, Sagiri opened it and spoke to him directly for the first time in a year, repeating the same phrase she had said when they first met: “Hello, Big Brother.”

What followed was a chaotic yet significant interaction. After a scuffle at the door and a comment from Masamune about the erotic nature of her illustrations, she hit him with a remote and slammed the door shut. However, she soon allowed him in on the condition that he not touch her revealing her guarded but softening attitude. During the conversation, Masamune suspected that she was the elusive illustrator “Eromanga Sensei.” Though she initially denied it, the misunderstanding led to another comedic outburst. Eventually, she began communicating through a microphone and speaker setup, and Masamune confirmed that her voice matched that of his mysterious illustrator.

Masamune expressed his wish to be a family again, to which Sagiri replied coldly that simply living under the same roof doesn’t make them one. She then forced him to leave the room.

Not long after, a classmate named Megumi gathered the entire first-year class outside Sagiri’s room in an attempt to get her to come out. Distressed by the situation, Masamune intervened and put a stop to it. Concerned for Sagiri, he rushed back to her room only to have her fling the door open and pull him inside, crying in fear over someone playing piano loudly outside. When Masamune checked the balcony, he discovered their eccentric neighbor, Elf Yamada, playing the piano nude marking the start of another unusual relationship in their lives.

Masamune Izumi
Sagiri is Masamune’s younger stepsister and secret illustrator. Initially, she refused to have any interaction with him, even avoiding meals and basic contact. Their relationship begins to thaw after she discovers Masamune is her writing partner. Despite her cold attitude at first, she gradually becomes more emotionally connected to him, showing signs of possessiveness and jealousy especially when other girls get close to him. Sagiri is determined not to be replaced as his illustrator and works hard to earn his acknowledgment. She admires Masamune both as a writer and as a person, eventually expressing deep affection for him.

In the first volume of the light novel, she mentions having someone she likes. By Volume 3, she reveals her dream of becoming that person’s bride. When Masamune confesses his longing for a true family after losing both his biological and step-parents, Sagiri agrees to be his sister “momentarily.” When asked if her dream is getting closer, she quietly replies that it’s getting further away implying her feelings are for Masamune. Throughout the series, it’s heavily implied that she does not want to be seen solely as his sister, though Masamune, due to a promise to their late parents and his own emotional walls, tries to maintain a familial boundary much to Sagiri’s frustration.

Megumi Jinno
Sagiri initially views Megumi as an annoying and intrusive classmate, especially resenting her closeness to Masamune. Despite her hostility, Sagiri agrees to meet with Megumi under unusual conditions blindfolded and tied so she can use her as a model. In a moment of impulsiveness, Sagiri removes Megumi’s underwear, causing her to cry. Feeling guilty, Sagiri removes the blindfold, apologizes, and speaks to her directly. Megumi is deeply touched by this and asks to be friends, though Sagiri refuses the title and instead offers her a favorite book to read, suggesting they meet again afterward. Their relationship becomes more cordial, though still awkward.

Elf Yamada
Sagiri respects Elf’s talent as a writer and is surprised when Masamune outperforms her in a competition. However, Sagiri never responds to Elf’s emails and is initially wary of her, particularly after Elf moves in next door. Believing Elf might replace her as Masamune’s illustrator, Sagiri grows jealous of their interactions. Eventually, the misunderstanding is resolved, but Sagiri remains firm in her decision not to work with Elf professionally.