Taiban!
English name: Tiny² Band Story
Type: ONA, Episodes: 7
Aired: Dec 31, 2020 to May 10, 2021
Source: Original
Rating: PG-13 - Teens 13 or older
Synopsis:
Mizuki Haruno, who has been spending her days feeling blue, was taken to a live concert by her childhood friend, Nozomi. She caught a glimpse of the "exciting world there."

"Nozomi...I want to play in a girls' band!"

The story of Mizuki who became a high-school student begins now! This is a rockin' youth story woven by the four individual girls from the music band at Hakumai High School in a town in Hokkaido!

(Source: Taiban! Official YouTube channel, edited)