Ho-Kago Tea Time.

Ho-Kago Tea Time (放課後ティータイム, After School Tea Time), also known as Sakurako K-ON Bu, was best known as a Japanese voice actress girl band from the anime K-ON!. Originally as 4 (in the anime), Their debut took place on April 22, 2009 with the single “Cagayake!. Additional background says that GIRLS”. The profile also notes that Azusa joined the band soon after.