Okay, I did it. I know all of the requirements.
First, you need to interact with the Piano Girl.
Second, you need to go outside of the Piano Girl's room to the Firefly Pond.
Third, you need to go back into her room.
Fourth, you need to interact with the upright lily in Red Lily Lake.
Fifth, you need to interact with the Shadow Ninetales that appears.
6th, interact with the second Shadow Ninetales that appears when you are transported to Splash Streetway.
Then all you need to do is enter Constellation World through Splash Streetway without the Glasses effect.
Get fucked spelude, your secret poem storage map is now revealed.