Mashiro Irodori is a third-generation VTuber affiliated with the Live-On agency and is also active as a professional illustrator. Her online persona is Haku Sakurabi. She is best known within the narrative as the creator of the avatar used by the protagonist Awayuki Kokorone, and she is the one who coined the nickname Shuwa-chan for Awayuki's unfiltered, drunken alter ego.

In terms of background, Mashiro is established as a skilled artist whose primary occupation outside of streaming is character design and illustration. She is responsible for designing the models of several other characters within the Live-On group, including Awayuki Kokorone and Shuwa-chan, indicating a high level of professional expertise and a central creative role behind the scenes.

Personality-wise, Mashiro presents a cool and sharp-tongued exterior. She often delivers precise, witty retorts and maintains a level-headed demeanor that contrasts with the more eccentric and boisterous personalities around her. This makes her a grounding presence among her gen-mates, who are largely prone to wild antics and over-the-top behavior. Despite this composed surface, she harbors a deep and genuine care for her friends. This affection becomes especially evident around Awayuki, where her guardedness softens. Her passion for art is another defining trait; when the subject of illustration or design comes up, she becomes noticeably more animated and enthusiastic, shedding her usual restraint.

Her motivations are primarily rooted in her close bond with Awayuki and her desire to support her friend's success. She is invested in Awayuki's growth as a VTuber and acts as a behind-the-scenes pillar, both through her professional work as an illustrator and through personal encouragement. She also exhibits a strong sense of responsibility toward her own creative output, taking pride in her designs and the characters she brings to life.

Role in the story is that of a key supporting character and close confidant to the protagonist. Mashiro serves as a collaborator in streams, a creative partner in designing new outfits and models, and a stabilizing influence in Awayuki's chaotic new life. Her insight and understanding of Awayuki's true nature, including the ability to tell whether Awayuki has been drinking simply by the tone of her voice, underscore the depth of their relationship.

The most significant relationship in her narrative arc is her friendship with Awayuki Kokorone. The two are extremely close off-stream, and Mashiro is often described as Awayuki's soulmate by fans within the fictional universe. This relationship is marked by mutual trust, frequent collaboration, and a deep, unspoken understanding. Mashiro also shares professional and friendly ties with other Live-On members, though her dynamic with Awayuki remains the most developed.

Character development is subtle but present. Over the course of the series, she becomes more openly expressive of her care for those around her, gradually allowing her sharp exterior to crack in moments of genuine warmth. Her confidence in her own art and her willingness to use her skills for the benefit of others continue to grow, solidifying her role as both a friend and a creative cornerstone of the group.

Notable abilities include her professional-grade illustration and character design skills, which are not merely a hobby but her primary occupation and a major contribution to the VTuber group's visual identity. Her sharp observational skills, particularly in regard to Awayuki's state, also set her apart. Additionally, she possesses the social ability to maintain a calm and rational perspective even in the midst of the group's many chaotic situations, making her an effective mediator and a reliable voice of reason.