The lights of the Seoul stadium glittered, a kaleidoscope of colours against the fading twilight. Backstage, the air buzzed with nervous energy and the sweet scent of hairspray. Density, the K-pop sensation composed of you, Sweet Tea Cookie, and Honey Cake Cookie but you weren’t only a K-Pop Band you all were also secretly hunters of the darkness but for now you all were had minutes from going live.

"Pumpkin Pie Cookie, are you sure this mic is calibrated right? My throat feels a little scratchy today," you said, forcing a cough into your hand. You tugged your jacket sleeve further down, red, intricate markings on your forearm throbbing slightly beneath the fabric. It was a constant battle, keeping the darkness inherited from your unseen father at bay, especially when your mother, Shimmer Cookie, had always preached light.

Pumpkin Pie Cookie, Density's ever-flustered manager, bustled past. "You're perfect, 'You'! Just take some more warm tea. The fans are screaming for you!" He was oblivious, as always, to the true nature of the girl group he managed.

Sweet Tea Cookie, ever graceful, smoothed her own stage outfit. "Leader, you're looking a bit pale. Are you sure you don't need a longer break?"

Honey Cake Cookie, already vibrating with excitement, added, "And that cough earlier during rehearsal… it wasn't just a tickle, was it?" She looked at you with knowing eyes. As a team, they understood the hidden battles, even if Pumpkin Pie Cookie didn't.

"Just nerves, guys," you lied, forcing a bright smile. On stage, the coughs could be dismissed as passion, or a quirk of your powerful vocals. Hiding the true reason, the way the dark energy sometimes flared when you pushed too hard, was a heavy secret.

Weeks later, the world was entranced by B.A.D.4, the rival boy band. Their new hit, "Bad and Dark," was inescapable. It played in every cafe, every store, transforming the mood of anyone who listened. But not in a good way.

Density was in their private practice studio, trying to choreograph a new routine, but the B.A.D.4 song was on repeat, its ominous bass thrumming through the floor.

"Did you notice how… off people seem after listening to 'Bad and Dark'?" Sweet Tea Cookie asked, her normally cheerful face clouded. "Like they're angrier, or just… less themselves."

Honey Cake Cookie shivered. "I tried to listen to it last night to understand their style, and I felt this chill, like something was trying to seep into my mind. I had to turn it off."

You paused the music, a wave of cold dread washing over you. The markings on your arm burned faintly. This wasn't just a catchy tune. This was an invasion.

"It's not just a song," you murmured, staring at the B.A.D.4 poster on the wall – T.N.T (Schwarzwälder) the leader and main vocalist, ZZ Skull (Licorice Cookie) the vocalist, Mushy P (Poison Mushroom Cookie) the rapper, and HellHound (Red Velvet Cookie) the choreographer. Manager Scarlett (Pomegranate Cookie) and Producer D.K.E.C (Dark Enchantress Cookie) loomed behind them, their faces chillingly familiar from old, forbidden texts. "This 'Bad and Dark'… it’s a broadcast. A dark enchanting current, spreading through the sound waves."

Sweet Tea Cookie gasped. "You mean… B.A.D.4 are actually The Cookie of Darkness? The ones focused on taking over the world?"

"In disguise, yes," you confirmed, clenching your fist. "This isn't about topping the charts anymore. This is about taking over the world via music. Producer D.K.E.C is Dark Enchantress Cookie herself." You looked at your teammates, a flicker of determination replacing the internal conflict. "We have to stop them. We have to save our fans, and the world."

The stage was set, not just for a concert, but for a battle. Density would have to perform the ultimate encore.