The student from Rainbow Locust No. 1 High School who appeared on the bridge was, of course, Su Bai, who had gone out after changing out of his pajamas. Perhaps because he already knew that something was indeed wrong with his memory, Su Bai wanted to fulfill his promises to Yao while he could still remember what they were.
Although Regulars in the Real World should not have been able to see Strange Creatures, if he wanted to bring every creature in the Vengeful Ghost Puzzle that wished to come out into the Real World, he still wanted to find somewhere he would not be disturbed, where he could fully enjoy his time with the puzzle pieces.
And so, after stumbling upon this abandoned park with its beautiful lake, Su Bai spent a pleasant stretch of time with the puzzle pieces who emerged from the "door." It was only as this "outing" drew to a close that Su Bai noticed other humans approaching their stretch of lakeshore.
If Su Bai could find this abandoned park, others could naturally come here too, so he was not particularly surprised. What did surprise him was that one of the distant figures seemed badly frightened, as though looking their way had revealed something a Regular would find hard to accept.
That person seemed able to see Strange Creatures.
People like that were rare, but they did exist. Otherwise, rumors and horror stories about "seeing ghosts" and "second sight" would not have spread so widely in the Real World. They were simply a rare breed, seldom encountered.
Just as Su Bai was about to go over and say hello to this rare specimen, he noticed the puzzle pieces beside him all making shushing gestures at the person, wicked expressions on their faces. To a Regular,