An ink cartridge includes a first case having a wall having a first end and a second end opposite the first end. The wall has a first opening and a second opening formed therethrough, the first opening has a first center, and the second opening has a second center. The wall also has a first center line and a second center line which is perpendicular to the first center line, and each of the first center and the second center is offset from each of the first center line and the second center line. The ink cartridge also includes a second case enclosed within the first case, and an ink supply portion positioned adjacent to the second end of the wall, in which a portion of the ink supply portion is configured to be received by the first opening. The ink cartridge also includes an opaque, protruding portion extending from the second case and positioned at the wall between the first end of the wall and the ink supply portion, and a portion of the protruding portion is aligned with the second opening.