In Nancy Drew: Shadow at the Water’s Edge, Nancy must snoop the cultural room (room 18) but will need a key to access the space when Takae is gone.
Use the EVP recorder to record the spot by the cherry tree in the garden, as mentioned in Savannah’s book. When Rentaro is gone from the shed (after 1am), you can set the recorder in the player sitting on the right shelf of the shed. Press the play button to listen in on a fight between Miwako and Yumi.
Yumi through something in the water. From the shed, cross the bridge in the garden to the other side of the water, and turn right to wade into it. Take a few steps towards under the bridge and you’ll find the key below.