Maria-sama ga miteru is a series that was already being hailed as a classic when I first watched it, yet one that took years longer than the slighter (and later) Kasimasi, to get an official English language release; I guess perhaps because it doesn't have wacky hi-jinks, just low key slice-of-life drama.
Set in a somewhat exotic Catholic school for girls, the story centres about first-year high school student Fukuzawa Yumi, and her incorporation into the succession for the school council, the Yamayurikai, or mountain-lily council (headed by girls with the titles of White, Red and Yellow Rose as one might not expect). This is done by "adoption", under the system where each girl adopts a member of the lower years as an honorary younger sister (in a sort of den-mother arrangement). While the somewhat uncertain relationship between middle-class Yumi and Sachiko, her hopelessly aristocratic onee-sama (top left) forms the core of the season, the stories of the other Rose "families" are visited as Yumi gets to know them; including, in flashback, appearances of the previous class of Roses.
I had forgotten quite how widely the back-story spread -- including, in flashback to the previous year, appearances of the previous class of Roses (lower left). I'd also forgotten that even in the first season we got fan-service in the form of Yumi's zettai ryouiki (top right), as well as quite how boisterous Satou Sei, aka Rosa Gigantea, was.
It definitely bore the rewatching; the more so to contrast with the series just past, set one year later, with Yumi now in the position that Sachiko is here.