Yumi is a first year student at the Lillian School for Girls, an exclusive all-girls Catholic school. The school has a tradition that older girls take a younger girl as their little sister or "soeur" in order to instruct and look out for them. Though Yumi admires Sachiko, a reserved second year student who is a member of the student council, she has no hopes of being chosen as her soeur. When an innocent encounter leads Sachiko to impulsively ask Yumi to be her soeur, Yumi is suddenly brought into the inner circle of the Roses, who are the members of the student council. With Sachiko at her side, Yumi begins to unravel and understand the relationships between the Roses and their soeurs and figure out her own feelings for Sachiko.
Hosokawa Kanako, a first year, sees Yumi as the ultimate embodiment of perfection. When preparations for the Hanadera Festival begins, Kanako tries to keep Yumi away from it due to her hatred of men and her fear of having Yumi be corrupted.Watch Now:Amazon
The Valentines' Day dates take place, with Chisato Tanuma finding Yoshino's card and Tōko finding Yumi's. During Tōko and Yumi's date, even more about Tōko's past is revealed, as well as her reasons for running away from home. They eventually visit the hospital owned by Tōko's grandfather, and Touko slowly starts to open up to Yumi. The season ends with Yumi's thought of Tōko accepting her rosary.Watch Now:Amazon
Lillian and Hanandera collaborate on a school festival, and Yumi tries to fix Sachiko's hatred for men.
The second year students go for a week's study-vacation in Italy. Yumi meets up with Shizuka Kanina while there.Watch Now:Amazon
The day of the Soeur Audition—turned into Tea Party—arrives, and soon the Kendo Competition, as well. Yoshino has been looking forward to the Kendo competition, but she has promised Eriko that she will have a petite soeur by then. Someone catches Yoshino's eye, but it looks like it might be more complicated than it seems.Watch Now:Amazon
Yumi and Sachiko finally go on their date to the amusement park. However, Kashiwagi and Yuuki turn up, with Kashiwagi bearing a certain agenda in mind. Yumi learns a few things and Kashiwagi's intentions are made clear.Watch Now:Amazon
Tōko suddenly shows up on Yumi's doorstep in a strange situation and ends up being over for dinner, while Suguru and Yumi have an agreement. As well, Rei and Sachiko have an understanding.Watch Now:Amazon
After Tōko realizes her large misunderstanding, crying, she is comforted by Noriko. The next week, the Valentines' Day Card Hunt for the Next Roses take place with surprising results. Sachiko and Tōko have an interesting conversation on the stairs, and eventually Tōko comes to realize something vital to her relationship with Yumi.Watch Now:Amazon
Lillian's School Athletic Festival begins, and Kanako and Yumi make a bet to settle the problems which began between them last episode.Watch Now:Amazon
This year's remaining, petite soeur-less en boutons, Yoshino and Yumi are feeling the pressure to find their little sisters, for various reasons. Yoshino suggests that they have a Soeur Audition to do just the thing.Watch Now:Amazon
The Yamayurikai Christmas party takes place. Tōko and Kanako are both invited to the party, but afterwards, Tōko rejects Yumi's offer of the rosary, and Yumi is crushed.Watch Now:Amazon
With the elections for the next year's Student Council approaching, Tōko unexpectedly enters the race with murky intentions.Watch Now:Amazon
Sachiko and Suguru Kashiwagi discuss Tōko's entry in the Student Council elections and her recent behavior towards Yumi. The Lillian Newspaper Club organizes another card hunt event for Valentine's Day, while Noriko worries that Yumi has given up on Tōko. As well, the Gigantea soeurs have a small discussion about the 'next Rose'.Watch Now:Amazon
As different people in her life try to help her find happiness, Tōko continues to run away from their support. Suguru warns Tōko that if she continues to run away, one day no one will chase after her. More details of Tōko's family situation and her reason for refusing to be Yumi's petite soeur are revealed.Watch Now:Amazon
Sachiko takes Yumi for a holiday in her summer home. While there, Sachiko's acquaintances make trouble for them.Watch Now:Amazon
Yumi and the Yamayurikai prepare a production (The Tale of Torikaebaya) for the upcoming school festival with neighboring boys school, Hanadera.Watch Now:Amazon
The day of the School Festival has arrived, there are many attractions but most importantly, the drama club is performing Little Women and Yamayurikai, The Tale of Torikaeba. With so much going on, the day might not just be another ordinary day.Watch Now:Amazon
Yumi and the rest of the Yamayurikai are invited for a female-only new year party, where Yumi has an interesting dream that could be applied to her current situation.Watch Now:Amazon
Yumi learns why Sachiko has been so distant lately. With newfound confidence, she promises never to question Sachiko's love for her again.
Yumi gets back onto her feet with different people helping her out. She learns that she must develop an identity outside of being Sachiko's petite soeur.Watch Now:Amazon
With graduation's onset, Sei and Shimako remember the events which led them to become soeurs in spite of their many complex obstacles and reservations. The two of them ultimately form a deep and healthy relationship without becoming codependent.
For Valentine's Day, the Lillian Newspaper Club organizes a treasure hunt in which the winners would get half-day dates with the en boutons. Yumi agonizes over what to get Sachiko for Valentine's Day, resulting in a spectacular misunderstanding between the two of them.Watch Now:Amazon
After a crying Yumi runs away from Sachiko's confrontation, Sei reveals the secret reason behind Sachiko's distress. The treasure hunt takes place with surprising results. and Yumi makes up with Sachiko in her own unique way.
Shimako falls into a depression after Sei graduates and cannot bear the weight of her secret alone. But a chance meeting with the down-to-earth Nijo Noriko gives her a new friend.Watch Now:Amazon
Yoshino takes advantage of her newfound health by joining Rei's kendo club, causing extreme worry on Rei's part and another roadblock in their relationship.