Kyōko Miyoshi is the 28-year-old homeroom teacher for class 2-B at Shiratama Middle School, recognizable by her dark purple hair and petrol-colored eyes. She teaches students like Asuna Harukaze, occasionally conducting unconventional English lessons involving suggestive or nonsensical phrases for exchange student Elizabeth Warren.

Beyond the classroom, Kyōko relaxes with beer, warm sake, cigarettes, and frequent post-school visits to hot springs. Despite a generally laid-back attitude, she supports the school's soft tennis club in her own unique way, sometimes appearing on the sidelines dressed as a cheerleader to perform small dances meant to motivate the team.

Her personality is cheerful, lively, and carefree. She often uses humor, puns, and playful teasing, particularly with Asuna, to lighten the mood. On the tennis court, however, she transforms, displaying intense focus, competitiveness, strong leadership, technical skill, and a distinct dislike for losing. Differing personality assessments exist: one identifies her as an ENFP and Enneagram 7w6 ("The Enthusiast"), emphasizing her optimism, pursuit of new experiences, avoidance of negativity, occasional distractibility, and difficulty with long-term commitments. Another classifies her as an ESFJ, highlighting her sociability, organizational skills, leadership within the tennis club, and tendency towards self-criticism under stress.