Chapter 1: The Shirt That Fits Too Well
The key turned in the lock with a slick, promising click. Mizuki pushed the door open, the weight of her grocery bags cutting into her palms. "I'm home," she called out, her voice softening at the edges with a hope she couldn't quite squash.
The smell hit her first. Instant ramen, the cheap kind with the overly salty broth, and underneath it, the sweet-rot scent of old energy drinks. The living room was a cave of clutter, lit by the jaundiced eye of a single floor lamp. Its glow caught the dust motes swimming in the air and illuminated the disaster zone: a leaning tower of crushed Red Bull cans, a game controller wedged between couch cushions, a whiskey bottle on the coffee table with a smudge of pink at its rim.
Her eyes skipped over the faded anime posters on the walls and landed on the couch.
Sukuna was slouched in his usual spot, a mountain of muscle and restless energy even at rest. His wild pink hair was a shock against the griminess of the room. He didn’t look up from his phone. "Took you long enough," he said, the words a familiar, grating bite.
"Sorry, the line was—"
A door down the hall creaked open. Footsteps, light and bare, padded across the cheap laminate.
Megumi emerged from the shadow of the hallway like a vision tailored specifically to puncture Mizuki’s chest. She was wearing a shirt. Just a shirt. It was huge, black, and obviously Sukuna’s, the hem hitting her mid-thigh. Nothing else. The thin cotton clung to the swell of her breasts, and Mizuki’s brain, traitorously efficient, noted the dark points of her nipples pressing against the fabric. Her legs were long and bare, vanishing into a scrap of black panties that flashed with every step.
"Kuna-nii," Megumi said, her voice a low purr completely devoid of sleep. She ignored Mizuki by the door as if she were a coat rack.
Sukuna’s head snapped up. A transformation wiped the bored aggression from his face, replaced by a warm, open focus Mizuki rarely saw directed at her. His crimson eyes lit up. "There’s my princess. Hungry?"
"Starving." Megumi drifted over to the couch and, without a hint of hesitation, curled herself onto his lap. She fitted herself against his chest, tucking her head under his chin. One of Sukuna’s arms curled around her waist, his large hand splaying possessively across her bare thigh, his thumb making slow, absent circles on her skin.
Mizuki’s fingers were going numb from the bag handles. She stood there, a polite smile frozen on her face. The groceries felt suddenly absurd in her hands—the fresh vegetables, the fish she’d picked out for dinner, the imported beer he liked.
"Megumi," Sukuna said, his voice a rumble in his sister's hair. "Manners."
Megumi turned her head, her spiky black hair brushing his cheek. Her blue eyes, sharp and dismissive, finally flicked to Mizuki. "Oh. Hey." It was flat. A procedural acknowledgment. She looked back up at Sukuna, her expression melting into something soft and proprietary. "The broth is too hot. You blow on it for me."
Sukuna chuckled, a rough, genuine sound. He reached for the ramen bowl on the table, pulling it close. He lifted a laden spoon, blew on it softly, and guided it to Megumi’s lips. "Careful, dumbass. Don't burn that pretty mouth."
Mizuki forced her legs to move. She walked to the kitchenette, the partition doing little to block the view. She set the bags down on the counter with a soft thud. The silence from the living room was dense, intimate. She heard the wet click of Megumi eating, a low hum of satisfaction.
"I got the spicy miso you like," Mizuki said, her voice too bright, slicing through the quiet. She started unpacking, just to have something to do with her hands.
"Not in the mood for it," Sukuna said, not unkindly, just distractedly. His attention was on the woman in his lap, on tucking a stray strand of hair behind her ear.
Megumi shifted, the shirt riding up higher. Sukuna’s hand on her thigh didn’t move an inch. "Nii-chan, my neck is stiff. From studying."
"Too much bad posture." His free hand came up, his fingers pressing into the base of her skull. Megumi sighed, a sound of deep contentment, and sank back against him. His touch was firm, knowing.
Mizuki stared at a bell pepper, its surface glossy and perfect. A knot, hard and hot, was tightening behind her sternum. This was wrong. The shape of it was all wrong. This wasn't brotherly. This wasn't how her brother had ever touched her, how any sane person touched their sibling. The possessiveness in Sukuna’s grip, the deliberate, lazy provocation in every move Megumi made—it coated the room like a film.
She made herself walk back to the living room entrance, leaning against the wall. "I was thinking we could watch that new series tonight. The thriller you mentioned."
Sukuna’s fingers were working up into Megumi’s hair now, massaging her scalp. Megumi’s eyes were closed, a small smile on her lips. "Maybe later. Megumi picked out some anime OVA. Gory shit. You’d hate it."
"It’s our date night," Mizuki said, the words slipping out quieter than she intended.
That got his attention. His crimson eyes cut toward her, sharp and impatient. "It’s Thursday. Date night’s Friday. Don’t be clingy, Mizuki." The insult was casual, an old endearment that now felt like a shove.
"Clingy," Megumi echoed under her breath, a whisper meant to be heard.
The heat in Mizuki’s chest pulsed. She looked at Megumi, at the blatant challenge in those blue eyes. She looked at Sukuna, at the way his entire world had narrowed to the space occupied by his sister. The evidence was in the intimate clutter: Megumi’s hoodie dumped on the couch, her hair tie around Sukuna’s wrist, the lipstick on his whiskey bottle.
"I just miss you," Mizuki tried, hating the plea in her own voice.
Sukuna sighed, a gust of irritation. He gave Megumi’s thigh a final pat and shifted, making to get up. "Fine. For an hour. Then we’re watching Megumi’s thing."
Megumi’s arm shot out, her hand pressing flat against his chest, keeping him seated. She turned her face up to his. "You promised. You said we’d finish it tonight." Her lower lip jutted out just slightly. "You always break your promises to me."
The change was instantaneous. Sukuna’s resolve, if he’d ever had any, crumbled. He settled back, wrapping both arms around her. "Alright, alright. Jesus. Don’t pull that face." He pressed a rough kiss to the top of her head. "Your pick. We’ll watch your garbage."
He glanced over at Mizuki, his expression flattening into a dismissive apology. "Raincheck."
Megumi twisted in his arms, smiling victoriously. She peeked at Mizuki over Sukuna’s shoulder, her gaze icy and triumphant. Then she nuzzled back into his neck. "Start it from where we left off. And no skipping the opening theme."
Mizuki stood by the wall. The frozen smile had finally fallen from her face. The ramen steam curled toward the ceiling. The amber light felt sickly, staining everything. She was a ghost in her own relationship, haunting the periphery of a space that had no room for her.
She watched as Sukuna reached for the remote, his body a cage of devotion around his sister. He didn’t look at Mizuki again. The opening guitar riff of some violent anime blared from the television, filling the charged silence.
The knot in her chest solidified into a cold, hard weight. This wasn't jealousy. It was something darker, a dawning, terrifying comprehension of the rules of a game she had never agreed to play. She took a slow step backward, then another, retreating to the kitchen where the groceries sat, forgotten and slowly warming in the heat of the room.