Milky Star

It all started under the treadmill. What remained of the obscene zeros was...! Yonggeun Health Club, a popular personal training shop in Seongwang-gu. The night classes, in particular, are incredibly popular, with male members flocking to sign up. The building owner, Seon Bin, discovers a strange foreign substance after a night class and investigates what's happening there. It turns out the night classes are a place for orgies disguised as exercise?! How dare you do this in my building... I won't let you do it!

(Source: Bomtoon, translated)