Instructions to get the achievement with images!
始める
Open the sandbox
To get to the sandbox go to the main menu, open extras, then go to scenes, it should be the first option.
Finding the cassette
So jump over this pile of rocks left of the wooden building, you should land on a ledge with rocks, sand and grass.
On the ledge should be this table with a cassette player.
Follow the edge of the ledge until you find a bush.
Inside the bush is the cassette, pick it up.
Put the cassette into the cassette player on the table you saw earlier.
わーい
Now just listen to the cassette, you should get the achievement soon! おめでとう!