Younger Sister’s Day, known as Imōto no Hi, is observed in Japan every September 6 to celebrate the affection towards younger sisters from siblings and family. The holiday was created by Japanese manga artist Kunio Hatada, who researched sibling relationships and noted that many successful women in entertainment and sports were younger sisters. Hatada chose the date based on astrology, believing that the astrological sign of Virgo represented the qualities of younger sisters. A notable event associated with this day is Japan’s Little Sister Grand Prix, which has featured winners like marathon runner Yuko Arimori. The celebration is also recognized by Japanese animation studios and streaming services, which promote titles featuring younger sister characters, such as the anime series Oreimo and Eromanga Sensei. People can participate in Younger Sister’s Day worldwide by giving gifts or sharing memories with their younger sisters on social media using the hashtag #YoungerSistersDay.