Heart Hibikase Theory

High school student Izumi is invited by a friend to go to a live music venue for the first time! However, when she nervously hands over her ticket to enter, she is told, "Junior high school students are not allowed." She soon bumps into a rude man, and during the concert she can't get into the music at all... Feeling down, the rude man calls out to her, saying, "Let me apologize"...!? Love resonates loudly inside the venue, and the heart rate soars in this love story between a live music venue manager and a grown-up high school girl! (Source: Comic Days, translated)