Meaning of "Old stuff"
It is slang referring to the BL (Boy's Love) genre, which depicts romantic relationships between older men and high school students.
"That webtoon has such a unique premise that I initially clicked on it thinking it was an erotic comic, but it turned out to be a completely different kind of story."
Related slang words
MomA neologism (slang term) used to describe individual investors—often referred to as "retail investors" in the stock market—who analyze the market like analysts and place a high value on evidence; it refers to individuals with an analytical mindset toward investing.CorrectA term used to briefly describe the act of acknowledging and agreeing with another person’s argument or statementCernilAn abbreviation for cunnilingus, referring to the act of stimulating a woman's genitals with the mouthHalf-and-halfIndicates that the answer is half right and half wrong, simply expressing that correct and incorrect answers are mixed togetherSpecies-specificA term referring to the unique and recurring characteristics or traits of a specific race, group, gender, region, etc.JeonrasThis is an abbreviation for "Former Radio Star" and refers to the YouTube variety channel launched by the duo Yoon Jong-shin and Shin Jung-hwan.PeriscopeThis is something people say to excuse being late or acting carelessly because they didn't get enough sleep.Gina-jeIt's a popular catchphrase used as a short way of saying "I'm sorry" if you've upset someone.