As First Astronomical Velocity get together at the Supernova studio to rehearse for an upcoming concert, Sonico is found allegedly 'murdered' inside a locked waiting room, though are relieved to find she had only fallen unconscious. Just then, Suzu's younger sister, Ena, appears, deciding she wants to investigate the mystery, coming up with ludicrous theories over who Sonico's 'murderer' is. They soon discover that Sonico's guitar has gone missing, which soon leads to Ena becoming implicated for the crime herself. In the end, they find the guitar on the stage and Sonico's fall was simply an accident. Later, after Sonico and the others take their leave, Ena confronts Supernova's maid, Miina, who had locked Sonico in her room to keep the others from discovering she had broken an amp.