Prim and elegant, Sachiko has a rough side and a very sweet side. She is very protective over Yumi and cares deeply about her. However, Sachiko often has the same problem as Yumi does — she does not share most of her problems with her sœur, causing many misunderstandings. Sachiko is slated to marry her cousin and fiancé Suguru after she graduates. This has caused her some distress since, because although she initially cared deeply for him, he did not reciprocate. They now have a complicated relationship.  Sometimes, Yumi must teach Sachiko how to live informally, for example, helping her select her first pair of jeans. Despite her sometimes stern appearance, Sachiko has her own share of insecurities regarding her relationship with Yumi, not to mention emotional insecurities rising from her home life; both her father and grandfather openly have mistresses, unabashedly dividing their time between home and the mistresses, which apparently led to her general disdain for men, as illustrated in the OVA series during a meeting with the student council members of Hanadera, an all-boys highschool.  After Sachiko enters her third year, she is now the new Rosa Chinensis. After the arrival of Touko, Sachiko spends more time with her than with Yumi, which makes Yumi jealous. Sachiko goes absent from school which makes Yumi worried. Later, Youko is sent to "bring" Yumi to Sachiko's grandmother house. Yumi finds out that Sachiko's grandmother recently died, which causes Sachiko to go into depression. Sachiko says that she apologizes for the past few weeks, and asks for Yumi's forgiveness; Yumi says that she loves her very much.  At the beginning of the summer holidays, Sachiko takes Yumi to her summer home. Whilst there, Sachiko's acquaintances make trouble for them. Yumi intends to leave, but Sachiko refuses. The acquaintances have a party, and invite them. At the party, they ask Yumi to play a musical instrument for Sachiko's great grandmother. Yumi says that she cannot play anything and prefers to sing the song "Maria-sama no Kokoro"; Sachiko accompanies her with a piano performance. The great grandmother is happy because the song brings back memories, and she asks Yumi to visit next year.   In the first season, Sachiko is Rosa Chinensis en bouton, her grand soeur was Mizuno Youko, and her petite soeur is Fukuzawa Yumi.  In the second season, Sachiko becomes Rosa Chinensis. 

At Lillian Girls’ Academy, a renowned all-girls Catholic school, pairs of girls become soeurs, or “sisters”, in order to support and guide each other during their time at school. The shy Yumi Fukuzawa thought she was far too ordinary to attract a soeur as popular and beautiful as Sachiko Ogasawara, but for some reason, Sachiko has set her sights on Yumi — but why does she want to become Yumi’s soeur, anyway, and just what will become Sachiko’s soeur entail? 
 
(Source: Maiden Japan)

[Profile](https://osawa-inc.co.jp/women/itomiki/)

The second season of Maria-sama ga Miteru. 
 
The spring term is beginning for the students at Lillian Girls' Academy. Friends are reunited, but for the Yamayuri Council, it's a bittersweet time. Yoko, Eriko, and Sei are busy preparing to depart Lillian while Sachiko, Rei, and Shimako are doing their best to ensure that their dear sisters receive a memorable commencement. 
Sei's departure will leave a sizable hole in the White Roses, and filling it won't be easy. But is there anyone who could appeal to Shimako enough to become the next Rosa Gigantea en bouton? 
(Source: RightStuf)

The fourth season of Maria-sama ga Miteru. 
 
Life for the young women at Lillian Girls’ Academy couldn’t be more exciting! The Yamayuri Council is working on a theater production with the all-boys Hanadera Academy, and the school festival is quickly approaching. But Yumi’s duties pale in comparison to the task assigned to her by Sachiko: choosing someone as a petite soeur! Will she be able to handle the pressure of such a monumental decision, or will Yumi crumble under the weight of the Council’s — and Sachiko’s — expectations? 
 
(Source: Maiden Japan)

The third season of Maria-sama ga Miteru. 
 
Summer has arrived at last, and with it comes the promise of summer break for the students of Lillian Girls’ Academy. Sachiko and Yumi retreat to the summer home of the Ogasawara family for a season of rest and relaxation, but their rosy trip soon sours when some old friends of Sachiko’s unexpectedly drop in. These wealthy snobs turn up their noses at Yumi and Sachiko’s relationship — and if Yumi isn’t careful, her blissful summer at Sachiko’s side could come to an abrupt and tearful end. 
 
(Source: Maiden Japan)

A series of specials included on the Maria-sama ga Miteru DVD releases.

Maria-sama ga Miteru's story revolves around the students of the Lillian Catholic school for girls, and can be considered character-driven, focusing on interactions between the characters rather than any sort of ongoing plot or goal to attain. At Lillian Girls' School, there is a tradition known as the sœur system (sœur being French for "sister" ) , in which a second, or third-year student, the grande sœur ("big sister" ) , will give her rosary to a junior student, the petite sœur ("little sister" ) , and promise to look after them and guide them.
 
When the story begins, Yumi Fukuzawa, a new first-year student admitted to Lillian, is praying in front of the Virgin Mary statue near the school entrance when she is suddenly approached by a cold second-year student named Sachiko Ogasawara who straightens Yumi's uniform ribbon. This seemingly simple act of kindness stays with Yumi the rest of the day, and she speaks of her meeting with Sachiko to her friends during class and lunch. After school is over, Yumi's classmate Tsutako Takeshima meets with Yumi to show her that she took a photograph of Yumi's meeting with Sachiko earlier that morning. Yumi asks if she can have the photo, but Tsutako says she will give her the snapshot under two conditions: one being that Tsutako can display it at the upcoming school festival, and two being that Yumi get Sachiko's permission to do so as well. Yumi agrees to this, which sets in motion a series of events involving the entire Yamayurikai — the student council of the school. A few weeks after first meeting Sachiko, Yumi accepts Sachiko's rosary and therefore agrees to become her petite sœur.
 
This officially inducts Yumi into the Yamayurikai where she assists them in school matters at the same level as the other two petite sœurs — Yoshino Shimazu, and Shimako Toudou — who are the petite sœurs of Rei Hasekura, and Sei Satou respectively. Through her activities in the Yamayurikai, Yumi becomes closer to the other members and generally finds her experiences with the group to be enjoyable.

A series of specials included on the Maria-sama ga Miteru 4th DVD releases.

A series of chibi-style "outtakes" from the "shooting" of the Mariamite series.

The setting is Lillian Academy, a private Catholic all-girls school where the student council is known as the Yamayurikai (Mountain Lily Council) and younger students are taken under the wing of older students through a system known as the "soeur system" ("soeur" is French for "sister"). The main character, Yumi, who is basically a nobody, suddenly finds herself interacting with the members of the Yamayurikai and their soeurs, most notably her crush, the talented, beautiful, and withdrawn Sachiko...
