2019-12-03: We regret to inform users that the archiver stack FoolFuuka&Asagi on Rbt.asia, Desuarchive, Archived.moe, and others are suffering reduced accuracy and missing posts in scraping 4chan. New, efficient, and more accurate scrapers are in the progress of development, but needs assistance and testing from C# .NET and MySQL/Percona developers to be ready for use. On behalf of all archivers, unless FoolFuuka&Asagi is replaced, we will now be unable to scrape properly under the strain of deep software inefficiency and unsustainable costs (like fireden). More details here.
Let me see if I can properly summarize the story without including the filler
Girl is born a quintuplet and as she grows she looks for her independence. In a fated meeting she finds this in a boy she meets on a school trip. The boy as well feeling down in life is also looking to be needed by someone. They spend all day together in Kyoto having a romantic date of sightseeing and playing where they end it with the promise of both turning their lives around for the better to benefit not just themselves but their mother and sister respectively. Before they leave Kyoto however the boy mistakes the girl's sister as her causing the girl, who was looking to have something special to herself, trauma. To prevent this from happening again she ramps up her efforts to separate herself from her sisters however her mother passes away causing more trauma. Now as much as she tries she can't get good grades so she looks for another way to be special in her athletic abilities, this causes her grades to fall more until she flunks out of school and has to transfer. To prevent her from being alone her sisters go with her sacrificing their position at the school and causing the girl more trauma. As fate would have it she is reunited with the promised boy at her new school and she sees he kept her promise with her. He doesn't recognize her and out of embarrassment for not keeping her end of the promise she keeps her real identity a secret with the plan to come clean after she continues to study with the boy and improve her grades. With this in mind she supports him in all of his endeavors in his job of tutoring her and her sisters. However she notices her sisters are starting to fall for the boy, preventing her from coming forward, as she laments she's at least thankful people like him as well. The girl then finds out that the boy has remembered her this whole time and he's found out that the girl he met is either her or her sisters.