Each of the four puzzles hold a secret. By discovering the secret of the word written on the back room, one can open a secret passage to a room with four items and a second room with a special message about the Unowns. These pics are courtesy of Pokémon Forever
The Keyword here is HIKARI. This means "light". Use "FLASH".

The items are:
Top-Left: Heal Powder
Top-Right: Energy Root
Bottom-Left: Gold Berry
Bottom-Right: Moon Stone

"Watashi-tachi
sotono Pokemon
zou isukuru."
The Keyword here is MIZU. This means "water". Have a Pokémon hold a Water Stone.

The items are:
Top-Left: Stardust
Top-Right: Star Piece
Bottom-Left: Mysteryberry
Bottom-Right: Mystic Water

"Karera-wa ishiki
sacchi-suru
chikara ari
soto kobamu."
The Keyword here is ANANUKE This refers to ANANUKENOHIME, or, ESCAPE ROPE. Use an ESCAPE ROPE. Upon re-entering the room, you'll notice the door opening.

The items are:
Top-Left: Heal Powder
Top-Right: Energy Powder
Bottom-Left: Berry
Bottom-Right: Psncureberry

"Watashi-tachi
ichizoku kotoba
kokoni kizamu."
The Keyword here is HOUOU This refers to HO-OH. Place Ho-oh at the head of your party, and the door will open.

The items are:
Top-Left: Revival Herb
Top-Right: Charcoal
Bottom-Left: Gold Berry
Bottom-Right: Mysteryberry

"Watashi-tachi
ningen-wa
karera-to tomo-ni
ayumu koto
hitsuyou
karerano tamenmi
watashi-tachi
tagidatsu."

 
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