Moeko Sekine attends Daijuni Middle School alongside classmates Kyotaro Ichikawa and Anna Yamada, progressing from Class 2-3 to Class 3-1. Her gyaru-inspired style features light hair, fashionable clothes, and a signature "cat smile." Academically capable, she once ranked fifth in her grade, defying assumptions linked to her appearance.

Outgoing and mischievous, Moeko often refers to herself in the third person and engages in playful teasing. She prods Ichikawa out of his shell while acknowledging his relationship with Yamada, even facilitating his entry into Yamada's apartment by posing as his girlfriend. Despite her teasing, she exhibits perceptiveness, recognizing Ichikawa and Yamada's mutual feelings early and subtly supporting their connection. Her relationships reveal complexity: she frequently clashes with Adachi Shou over his perverted tendencies, yet shows vulnerability, blushing when he complimented her generosity after White Day. Underlying tensions exist with Yamada, culminating in a study camp incident where Moeko expressed frustration over feeling overlooked, leading to mutual understanding and a strengthened friendship.

Moeko belongs to the cooking club with Andou Kanna, specializing in hamburger steak and omurice. Her interests include pink and black, cats and rabbits, Disney's Tangled, and mainstream anime like Re:Zero (favoring Ram over Rem), influenced by her otaku older brother. She enjoys Frappuccinos and admires celebrities Miracham and Kouda Niko. Character development occurs through emotional conflicts, such as her study camp outburst showcasing insecurities and a desire for recognition, which fosters growth in her friendships.