Remember that this special premiered in theaters in Japan on July 14th, and the description writes:

• “Gotoubun no Hanayome~” is an adaptation of an arc not shown in the main series. With only six months left before Futaro and the Nakano quintuplets' school years are over, summer vacation is about to begin. Futaro tells his sisters that he'll be taking a break from tutoring during the holidays to focus on studying for the upcoming college entrance exam. The sisters are sad that they won't be able to see him for a while, but suddenly they receive a call from him.

On the other hand, Negi Haruba published the manga in the magazine Weekly Shonen Magazine from the publisher Kodansha between August 2017 and February 2020, with a total of fourteen compiled volumes. The work inspired two anime seasons and a film that concluded the story. The work inspired a twelve-episode anime adaptation produced by Tezuka Productions and debuted in Winter-2019 (January-March)followed by a second season in Winter 2021 (January-March) and a film in May 2022, both produced by Bibury Animation Studios.

Production team

• Yukihiro Miyamoto (Mahou Shoujo Madoka☆Magic, Nisekoi, Denpa Onna for Seishun Otoko) was in charge of directing this special in the studios STEMreplacing Masato Jinbo already Bibury Animation Studios.
• Keiichirou Oochi (Hikikomari Kyuuketsuki no Monmon, Uchi no Kaisha no Chiisai Senpai no Hanashi, Megami no Café Terrace) returned to take over writing and supervising the scripts.

Synopsis of Gotoubun no Hanayome

Fuutarou Uesugi is an excellent high school student, but he leads a difficult life. His aloof personality and reclusive nature have left him friendless, and his father is in debt, forcing his family to fight for survival. One day, during lunch break, Uesugi gets into an argument with a transfer student who has claimed "his place," causing them to dislike each other. That same day, he stumbles upon a golden opportunity to pay off his family's debt: a job tutoring the daughter of a wealthy family, with a salary five times the market rate. He accepts the offer, but is horrified to discover that the client, Itsuki Nakano, is the same girl he confronted earlier!

After unsuccessfully trying to gain Itsuki's approval, Uesugi discovers his problems don't end there: Itsuki is actually a quintuplet, so in addition to her, he must also tutor her sisters: Miku, Yotsuba, Nino, and Ichika. Despite the very real threat of failing, they want nothing to do with a tutor. However, their family's livelihood is at stake, so Uesugi presses on, steadfast in his determination to rid his sisters of their hatred of studying and successfully lead them to graduation.

Source: Comic Natalie

(c) Negi Haruba/Kodansha Production Committee/Movie “The Quintessential Quintuplets”