Lumo

The SD card is located in the room behind the locked door near the start of the game (the corridor with the red arrow painted on the wall). It is the FIRST story based item you must collect in order to proceed, making this unmissable.

Follow the game through the relatively linear opening section, collecting the agility orb, first map, wrench, activating the conveyor belts, key, the second map and then back to the locked door.

Inside is a four storey crate tower, with the SD card at the top.

Run to the love box (companion cube, anyone?) And climb on it so you're at the rear of the tower, the north side. Jump into the darker box on the third storey from this position and you will slide it out from underneath the crate on which the SD card rests. Push it as far as it will go, and then make a slightly fiddly leap from out of the little space you find yourself in onto the box you just moved. You will fall a couple of times, but just leap straight back into the gap from the love box.

From here, it's just a quick leap to your prize.