Aka no Sekai

Regulus is a cool, introverted young man forced to participate in a summer camp by his mother. Regulus is more nervous than elated–outdoor activities force students to interact more. Despite his efforts to stay on the fringe, Regulus is caught up in trouble when a classmate paints a room an eerie, deep crimson color, sparking a huge disturbance. Contains 4 loosely links oneshots. (Source: the manga habit)