GA Geijutsuka Art Design Class: Slapstick Wonderland

Inside an airplane heading for Japan, Mari is clutching a sketchbook which once belonged to her grandma, who is now deceased. The sketches on it are what her grandma had drawn before she died, reminiscing about the days spent in Japan. To color the sketches: a promise Mari made with her grandma. What will be Japan like, the country the grandma so much loved? Feeling hopes and fears, Mari drifts off to sleep. The place she is heading toward as a short-term international student is GA (Geijutsuka Art Design Class). What kind of story will unfold, casting Mari and the members of GA?