It's Barnaby Gumball's junior year at A.A.A. without his best friend at his side. But when he ends up becoming the new music teacher, everything changes. Follow Barnaby and Marshall Lee on their journey of being in a relationship, coping with mental illness, and self discovery in Teaching Nostalgia! (❗️Trigger warning: depression, OCD, reference to abuse, reference to rape, suicide attempt, drugs, alcohol, etc.)