Houki Shinonono enters her first year at the IS Academy, reuniting with her childhood friend Ichika Orimura after a six-year separation. Her family operates a shrine and kendo dojo, where she cultivated an early passion for kendo, achieving victory in a national tournament shortly before the main story. This win held personal significance due to Ichika's promise to become her boyfriend if she succeeded. However, she couldn't claim this promise; her family entered government protection immediately after her older sister, Tabane Shinonono, revealed the Infinite Stratos exoskeletons to the world. This event fueled Houki's resentment towards Tabane for disrupting her life and abandoning the family. Shaped by her upbringing, Houki displays a stern and disciplined demeanor, yet grapples with emotional instability and social difficulties. The separation from Ichika intensified these struggles, causing her to channel frustration into kendo rather than using it for self-control. She exhibits a quick temper, prone to violence, jumping to conclusions, and stubbornly refusing to admit fault, sometimes acting hypocritically – such as rejecting her connection to Tabane while accepting the Akatsubaki IS unit from her sister. Beneath her gruff exterior lies a fundamentally kind nature; she values friendships with fellow female students, though she competes with them for Ichika's attention. Childhood bullying left her with low self-confidence about her femininity and appearance, making her uncomfortable in revealing clothing. Romantic feelings for Ichika drive much of Houki's growth. Initially cold towards him to mask her emotions upon reuniting, she gradually becomes more open, though jealousy remains a frequent reaction. During the *Infinite Stratos Encore: Sextet of Burning Love* festival at her family's shrine, she attempts to confess to Ichika amidst fireworks, but the noise prevents her words from reaching him, highlighting her persistent struggle to express her feelings directly. As a kendo practitioner, Houki employs an offensive fighting style and possesses abnormal physical strength, demonstrated when she dented a locker in an emotional outburst or shattered an opponent's defense with a regular sword. She initially pilots the training IS Uchigane before receiving the fourth-generation Akatsubaki from Tabane, equipped with twin katanas and the energy-replenishing *Kenran Butō*. She also briefly wielded Akatsuki, an IS capable of suppressing other units. Using Akatsuki, she severely injured Chifuyu Orimura and her IS before the main series; the resulting guilt overwhelmed her, leading Tabane to seal her memories of the event. Her IS compatibility rank fluctuates dramatically from C to S, heavily influenced by her emotional state and connection to Tabane. After an incident where her jealousy caused Akatsubaki to malfunction, resulting in the loss of both Akatsubaki and Akatsuki, she returns to being a regular student but resolves to face her problems maturely. Houki's relationships extend beyond Ichika. Her dynamic with Tabane remains strained, layered with unspoken guilt and responsibility on both sides. She regards Chifuyu Orimura as an elder sister figure and shares information about Tabane with her. Initial clashes with students like Cecilia Alcott and Laura Bodewig evolve into alliances, with Houki collaborating with them in combat. Her interactions with Tatenashi Sarashiki stand out; Tatenashi's demeanor reminds Houki of Tabane, fostering a complex, less confrontational rapport. Her development culminates in acknowledging past mistakes, particularly concerning the Akatsubaki incident and her treatment of others. Accepting her role as a regular student without her IS units, she commits to self-improvement and supporting her friends more constructively.