Mobuko Sonota recurs as a participant in the Tesaguri club's experimental activities. She possesses multiple identical sisters, sextuplets born over three consecutive years, who frequently assist the club during brainstorming sessions. These sisters collectively serve as participants or opponents when the main characters test unconventional club ideas.

Her most notable contribution occurs in the first season's baseball-themed episode. The Tesaguri club devises a blindfolded baseball game where Mobuko and her sisters form the opposing team; players rely on verbal guidance from teammates due to the blindfolds, resulting in chaotic outcomes including property damage. In a football-themed session, Mobuko proposes a rule requiring players to recite haiku upon receiving the ball, with poor poetry triggering penalties like yellow cards or conceded goals.

During a shogi club experiment, Mobuko's sisters help create a giant shogi board where players physically contort under Twister-inspired rules to maintain positions and move pieces. Mobuko herself proposes a cheerleading club concept centered on performing cheers at absurdly inappropriate events like funerals or jury trials.

In a karuta card game experiment, the club uses embarrassing photographs of the main character Koharu as cards, featuring participation from Mobuko's sisters. Information regarding her background, development, or appearances is limited to these episodic interactions.