In Amberground, a dangerous terrain where a man-made star casts a permanent twilight, young Lag Seeing aspires to become a Letter Bee: a postman entrusted to deliver the hearts of people separated from the ones they love.

    Enraged, Tsukasa puts the dreaded red tag in Tsukushi's locker — a sign that she is now a target for the abuse of the F4 gang and the entire school. But when Tsukushi fights the gang with their own weapon, Tsukasa finds himself falling for her!