How To Get a Complete Stranger To Smile

Les Amis de l'ABC is a group of college-aged students, a rag tag team that meets at the cafe Musain a few days a week. Their leader, Enjolras is always seeming to be committed to his work while remaining serious and stoic. When a street artist begins decorating the sidewalks and walls near ABC with words of mockery, he doesn't seem to notice. The other members, however, do. The anonymous artist always signs their works with a single letter, "R". Enjolras says to leave it alone, but a few members can't help but try to figure out who's doing it and why.
(Modern AU, Musichetta runs the cafe, they're all in college with the exception of Musichetta and Gavroche. A few of the Les Amis work at the cafe, etc. Kind of cliche, heads up!)