The Box Storage area is a side tunnel that branches off of Level 33 of the Main Tunnel, along with the M-Tunnel. It consists of eleven levels, all of which can be played with any character. However, the first part of the Angel Missions takes place in the Box Storage Area, part 11, and thus can only be played with the Angel. Several people contributed levels to the Box Storage Area: mathwiz100 (1, 8, 10), portugal2000 (2, 7, 9), Farkss (3), max_blue_01 (4), and Karsh777 (11).
The Box Storage Area has many boxes in every level, hence the name. Most of the levels have the boxes arranged in symmetrical, aesthetically-pleasing patterns, while others have the boxes spread out in small clusters throughout the level. The player is often required to jump over gaps from one box or cluster of boxes to the next.
The following is a brief description of the story in the Box Storage Area. More information on the story can be found here.
After beating the Box Storage Area, the cutscene 'My Turn' will begin, featuring the Runner and the Angel. The Angel demands that the Runner give him her map, saying "It's not like you're using it." He goes on to complain that she's had more than enough time to find a way back home, and asks for the map once again. The Runner protests, "How come everyone already wants to go home?" revealing that she has no desire to go back to the Planet yet. This cutscene marks the beginning of the Angel Missions.
Later on, during the Bridge building side-quest, ringed boxes can be found in parts 1, 6 and 7 of the Box Storage Area. The cutscenes 'Something Weird' and 'Lightning Strikes Twice' also take place in the Box Storage Area, in parts 6 and 1 respectively. 'Something Weird' describes how the Student discovers the first ringed box, and 'Lightning Strikes Twice' depicts the Student showing the second ringed box to the Runner.