Koiochi Flag

In November 2020, SKE48 announced the release of the single, "Koiochi Flag" to commemorate the graduation of member Jurina Matsui.[1] It is a pop song with lyrics about friendship.[2] The single was made available digitally as an EP, on February 3, 2021, by Avex Trax.[3][4] The physical version was also released the same day in three editions: Regular, First press limited, and Seven net limited. Each edition was made available in CD+DVD formats in three types: A, B, and C; each type contains the single "Koiochi Flag" on the A-side. Additionally, type A includes "Memories 〜Itsunohika aeru made〜" and the instrumentals of both tracks on B-side, type B contains "Change Your World", while C has "Anogoro no rokkā". The DVD features music videos and bonus videos of the tracks. A live version of the single, which includes "Koiochi Flag" and "Oto no wareta chaimu" was released in Japan.[3]

"Koiochi Flag" was a commercial success in Japan. The single took the number one spot on its first day of release on Oricon Daily Singles Chart, selling 5,188 physical copies.[5] The single peaked at number one on the Oricon Weekly Singles Chart, on the chart issue dated February 9, 2021, selling 191,000 copies in its opening week.[6] It became SKE48's 23rd consecutive chart-topper, making them the fifth female artist in history to achieve this.[2] It has been certified platinum by the Recording Industry Association of Japan (RIAJ) for sales exceeding 250,000 copies.[7]

"Koiochi Flag" sold debuted at number one on the Japan Hot 100 chart on February 10, 2021, selling 17,897 digital downloads.[8] The single recorded 196,556 copies in the tracking week, which was highest sales for that week.[9]

The accompanying music video premiered on SKE48's YouTube channel on January 12, 2021. The video shows the members performing choreography in multiple groups.[10] To promote the song, the group performed it live on the release day.[11]