Polaris wa Kienai

Two years after the death of the the idol Sora Tajima, who was the center of the idol group Polaris, people have been gradually forgetting her. High school girl Mizuumi Tachibana can't accept this and does the impossible in order to prove the existence of a "God." In a world where likes are everything, she creates the eternal idol.

(Source: Square Enix, translated)