You stumble into a secret passageway from Emilylowes's blog

Head through the gate and into an area that opens out on your right, defeating your second bank of brigands Lost Ark Gold. You’ll find an ingredient for Miner’s Rum in a sack on the floor here, near a broken mine cart against the northeast wall. And if you follow the wall just a few steps east you’ll come across a secret passage in the wall. It can be tricky to find, but just keep clicking on the wall until you move into it.

Follow it into a small clearing where you’ll find two mokoko seeds, one on either side of a raised dais, both partially hidden in the grass.

Once collected, grab the lantern of fireflies from the dais. These will appear in your quest item inventory.

Mokoko Seeds Four And Five – Second Secret Passageway

Now, move back to the area in which you had the first battle and found the first seed. Head to the left side of the gate this time and follow the edge of the map backwards. Go past the rails and the red banner, hugging the north wall, and you stumble into a secret passageway. It’s behind some crates if you haven’t already destroyed them. Follow the left-hand wall as the passageway turns north and you’ll find the second mokoko hidden in the grass at the base of some yellow flowers before you get to the glowing dais.

Next, move to the statue, and the scene opens out to reveal a small platform in the water to your northeast. On that platform will be another seed. As long as you’ve picked up the lantern of fireflies Lost Ark Gold for sale, you can now interact with this dais. A glowing path of fireflies will appear across the water, allowing you to walk across and collect your fifth mokoko.