In short, it was a small misunderstanding.
Sheng Feinan and Feng Liusi's encounter with Casio was different. After the three of them got lost around a corner, Sheng Feinan had been alone all the time.
He never ran into the Scales Monster in disguise.
So all along, he thought that the relic's mechanisms had inadvertently separated the three of them, leaving each of them isolated.
He remained on guard throughout the journey and encountered no dangers. The only issue was getting a bit lost due to changing passageways. After wandering around for half the day and finally finding his bearings, he met up with the others.
Unexpectedly, Casio suddenly attacked, unleashing almost a full-strength punch.
His specialties were swordsmanship and whip handling, and his strength and speed could not compare to Casio's, not to mention his rushed attempt at blocking. As a result, he was unable to block the first punch, leading to a deeper level of misunderstanding.
