King of Prism by PrettyRhythm (2016) Online
The completely male musical group 'Over The Rainbow' succeeds in its debut. Aiming to become the best boy band, more students enroll in Edel Rose (school). Hiro and the others begin practice for the Prism King Cup the ultimate test for music groups, an event that is held once every four years. However, a rival bands called "Schwarz Rose" appears... Who will become the Prism King, the one who can make girls' hearts throb the most!?