My Little Sister is My Diehard Fan

In their youth, Shirabe Yamada encouraged her brother Minoru to become a mangaka, but years later, and now that she's a high-school-age streamer, she can barely stand him. Now a university student and amateur mangaka, Minoru does his best to keep his craft a secret from her, but on the day his manga is canceled by the publisher, Shirabe accidentally discovers his studio in his room and that he's the mangaka 'Aoi Ringo'.
Shirabe then confesses to him: she's Aoi-sensei's dying fan. Now somewhat on the same page, the siblings do everything in their power to keep the manga running!