Sanae Minami presents as physically frail and chronically shy, possessing a notably younger appearance than her peers. She has black hair, violet eyes, a pale complexion, and a slim build, standing 145 cm tall. Her weak constitution requires regular medication, which she initially passes off as vitamins. Doctors suggested her relocation to Kanenone, believing the rural setting and fresh air could improve her health.

Her personality is defined by profound timidity, reserve, and anxiety, especially around male classmates. She shuns social interactions and rarely approaches others. This vulnerability, coupled with her childlike look, draws the unwanted fixation of Taizo Tenjin, who aggressively pursues "little sister" archetypes. His persistent advances consistently frighten her, deepening her apprehension toward boys. Despite her general reticence, she forms a trusting bond with Yuusuke Takasaki after he assists her, suggesting nascent romantic feelings. She also cultivates a close friendship with Wakaba Kutsuki; their shared naivete and Wakaba's encouragement help Sanae gradually emerge from her shell, allowing them moments of lighthearted interaction.

Her documented narrative remains centered on her health challenges, cautious social integration, and reactions to Tenjin's harassment and Yuusuke's kindness, without significant evolution or expanded background in additional media.