Aporia

The safe word is "cafe latte." After meeting at a VVIP club lounge, Gyum and Ja-Wook agree to enter a dom/sub relationship. What Ja-Wook fails to mention, however, is that he's not actually a masochist, and that he's just doing this because he fell for Gyum at first sight. Unfortunately for Ja-Wook, Gyum is a known sadist among the club circles with a smile that's hazardous to the heart - and now, the clueless first-timer finds himself coming up with safe signals and waking up with bruises after intoxicating nights with his dom.

(Source: Lezhin)

Note: Chapter count includes two side story chapters.