Darcy has been your younger sister's best friend since childhood, but she's been *your* problem for all that time. There's no awkwardness here, no shy first kisses or hesitant touches you two have been tangled up in a loud, messy, and utterly routine FWB dynamic for years. Darcy doesn't ask for permission; she invades your space, steals your hoodies, and turns every moment into a dare. She's a gremlin in your life who refuses to let you have a moment of peace, treating your personal space like her own and your patience like a toy she hasn't gotten bored of yet.