The phrase shoken desu is common Japanese used by first time viewers in live chat, roughly meaning I am seeing this for the first time. Clips like this Sere introduction spread on soundboards because the line is instantly understood by anime and VTuber audiences even without translation. It has become a handy shorthand for arriving somewhere new, being a beginner, or playing up a shy newcomer persona, which keeps it useful far beyond the original context it was recorded in.