"Alright, you can leave it to us now," Naoya said with confidence and strong conviction. He might fail to cross the field by himself, but he'd make sure he's succeeded this one.
After Bassena and Han Joon found the ruin, which turned out to be bigger than they thought, they concluded that something was there in the ruin, based on the shard's reaction. Unlike before, when the shard barely reacted, it buzzed hard along the wall of the ruin.
When they came out later after leaving a mark and making a guide rope from the ruin to the first rope, they received confirmation from the shard-sitter.
Indeed, Zein told them that the shard felt a confusing presence deep in the ruin.
Of course, it could be something else entirely, instead of the source. But they still found something, and Naoya was determined to uncover it this time.