You can start this substory during Guldo’s Claim to Fame, right after you get a Dragon Ball from Vegeta and move hiding spots with Bulma. The tourist couple is visiting every planet they can and finally arrived on Namek. Completely oblivious to the current ongoings with Frieza, they say they’re not going to leave until they get their hands on something called Maristone, so that’s where you come in. Head to the marker to find a general circle for the location of the Maristone, but even if you search every inch, you’ll never find it. The reason for this is because it is not in plain sight, but is actually hidden.

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(1 of 2) Destroy the hill here

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Destroy the hill here (left), and you will uncover the Maristone (right)

Locate the small island along the river and fire a couple of Ki blasts at the hill there. This will destroy the hill and if you use your Ki search, you should find a purple orb, which turns out to tbe the Maristone. Bring this back to the tourist couple to see some of Frieza’s forces harassing them. This leads to a battle with them, so take them out (still to the cluelessness of the couple) and the substory will be over.