Maria-sama ga Miteru 3rd follows the final season of the series, set during the students’ summer break at Lillian Girls’ Academy. Sachiko and Yumi head to the Ogasawara family’s summer residence for a restful holiday, but their joy is interrupted when old acquaintances of Sachiko’s unexpectedly appear. The affluent visitors snub Yumi and Sachiko’s relationship, and if Yumi fails to navigate the situation, her idyllic time with Sachiko may end abruptly and tearfully.