After you go southwest from the Ukouh Shrine, you reach the In-Isa Shrine.

Obtain Fuse Ability

When you enter the In-Isa Shrine, there will be a cutscene. After the cutscene, you will get the Fuse ability.

Fuse a Weapon

Go straight ahead and take the Rusty Claymore, and equip it. Then use the Fuse ability on one of the nearby boulders, and press the indicated button to fuse the Rusty Claymore to it. Swing the fused weapon at the stone barrier in the doorway to break it down.

In the room up ahead, look at the top of the stone columns to find one that has a chest on top. Hit the column with the fused weapon and open the chest to get five arrows.

Fuse Arrows

There is a locked green door ahead, so go down the other hallway and take the Fire Fruit from the trees. Draw your bow and follow the on-screen instructions to fuse a Fire Fruit to it. If somehow you run out of fire fruit, you can draw your bow and walk over to one of the torches in the corner to light the end of the arrow.

Then look up at the far wall and shoot a fire arrow at the leaves on the wall. After a moment, the chest will fall down below. Open it to get a Small Key.

Unlock the Door

Go back to the locked green door down the other path and check on it to open it with the small key that you obtained.

Battle

A Captain Construct will attack. You can shoot a fire arrow at the leaves under it to damage it. Defeat it and take the Construct Bow that it drops. It also drops a Rock Hammer that it created. There are some additional weapons and fire fruits on platforms in the corners of this room.

Receive the Light of Blessing

Use the Boulder Hammer on the stone door ahead to break it down, then go forward and check on the glowing object at the end to receive another Light of Blessing.

Receive an Energy Cell

After you leave the shrine, a Steward Construct will give you an Energy Cell.

Go to the Steward's Associates

The Steward showed you a cave where you can find others who can teach you how to use the Energy Cell, so go in that direction.

Battle the Soldier Constructs, and feel free to take the Board Guster that one of them drops. Then look for the treasure chest near the cookpot and open it after you defeat the Soldiers to get a Soldier Reaper.

Then go into the cave. This is the Pondside Cave.