After completing The Sun-Wheel and Mt. Kanna, white illusions will begin to show up around Tsurumi Island. Many of them are characters that players have met in the past—including Ipe, who had been involved in various parts of Ruu's story.
Meet Ipe, now an indistinguishable illusion, once again in Chirai Shrine. His exact location is marked up in the image below.
He's on his way to board the boat away from Tsurumi Island, but he lost an important charm that Makiri gave him. He believes he lost it while fishing somewhere on the isle west of Autake Plains.
The exact location of the fishing spot is circled in the image above. Upon heading to the area, you'll find a Thunderbird Statue by the shore, with a monster camp nearby. Use the Peculiar Pinion Gadget on the Thunderbird Statue to reveal a fishing spot.
Try your luck at fishing until you obtain the Quest Item called Makiri's Charm. This part of the Objective is completely luck-based, so you might get it on your first try or not until your fortieth try. Remember that you can change the Time on the main menu to spawn different fishes in the day and night. But after all the fish have been caught, you'll need to wait three real-time days for them to respawn.
After obtaining Makiri's Charm, head back to Ipe in Chirai Shrine and hand it over to him, completing the Hidden Exploration Objective. You'll be rewarded with a Precious Chest.
Check out our guide on How to complete Rero’s Hidden Objective in Genshin Impact, another part of the overarching tale of white illusions in Tsurumi Island.