Chapter Text
Months had passed since that first real kiss in the entrance. They hadn't put any big labels on it or made a dramatic announcement—not even to each other. They simply…were. Kisses that started softly and ended deeply on the sofa in Gen's apartment, caresses that lingered on the waist or the nape of the neck without haste, hands that sought each other under the covers while they watched bad movies.
Senku no longer blushed every time Gen called him by some cheesy nickname in a low voice; he just rolled his eyes and responded with a kiss, romantic words not being his strong suit.
Senku's friends—Chrome, Kohaku, Taiju, and Yuzuriha—had noticed the change a while ago. The questions started subtly ("Who's the person who's been distracting you so much lately?"), then became direct ("When are you going to introduce us?"). Senku always dodged the question with the same curt reply: "There's nothing to introduce. It's just someone." It wasn't distrust; he trusted them to keep the secret if necessary. It was that he liked exactly what they had now: calm, privacy, the feeling that the outside world didn't need to interfere yet in something that was still slowly developing.
Gen understood. He never pressured him. He just smiled when Senku told him, "Not yet."
One Thursday afternoon, Gen left rehearsals early. The director had canceled the last hour due to a technical problem, and Gen didn't hesitate: he grabbed his backpack, put on a baseball cap and a scarf even though it wasn't that cold, and drove to Ishigami's apartment. They were used to meeting there; Senku didn't have a driver's license yet (he'd be eighteen in a few months), and Gen's apartment was too far for Senku to walk home alone at night. Byakuya always greeted them with tea and a joke, and Gen had grown accustomed to the smell of home and the former astronaut's easy laughter.
When he rang the doorbell, he expected to see Senku open it with that 'you got here sooner than I said' look and a quick kiss before Byakuya appeared. Instead, it was Byakuya who opened the door, frowning and with an expression that mixed stress and urgency.
"Gen," he whispered, almost yanking him inside. "Quick, come in."
Gen blinked, confused.
"Is something wrong?" Byakuya carefully closed the door and gently pushed him toward the hallway that led to Senku's room.
"There's one of Senku's classmates here. Luna. They have to do a group project for literature class. We weren't expecting visitors and… well, you're not undercover today. If she sees you, she'll recognize you in two seconds."
Gen's eyes widened in surprise. Senku never did group projects, though it wasn't uncommon for him to be forced into them sometimes. And this Luna girl… he'd never mentioned her, probably too engrossed in his own notes. Byakuya led him to Senku's bedroom.
"Stay here for a while. Senku's in a bad mood because he hates group projects, and Luna… well, she's Luna. I'll let you know when she leaves." Gen entered the room without protest. The door closed behind him with a soft click. He stood for a second, processing: the desk covered in prototypes, the unmade bed, Senku's scent everywhere. He smiled despite everything and sat on the edge of the mattress, taking out his phone to send him a quick message.
Gen
I'm hiding in your room like a thief.
Your dad forced me in here.
Is everything okay?
There was no immediate response, which made him a little uneasy. It was illogical; his boyfriend was only a few feet away, but he could hear Senku's phone receiving his messages, which meant he knew it was him writing (it had a special ringtone), and yet he still couldn't reply.
Gen approached the door and carefully pressed his ear against it. The voices were muffled, but clear.
Senku's voice sounded tense and sharp.
"...and that's why the symbolism of the color red in the novel is obvious. It represents passion, danger, death. We can divide it like this: you do the secondary characters' parts and I'll do the protagonist's. We'll finish in an hour and that's it."
The girl's voice—Luna, Gen guessed—was high-pitched, lively, almost sing-song.
"Oh, Senku, always so direct... I love how you explain things! You're so smart. Did you know you're the only one in the class who really understands these deep concepts? The others just copy from the internet."
Senku snorted audibly.
"It's not a big deal. I only read the book." Byakuya chimed in from the kitchen, trying to mediate.
"Guys, do you want something to eat? I have some freshly baked cookies." Luna giggled.
"Oh, Mr. Ishigami, you're so sweet! Senku is lucky to have such a caring father. I wish I had a father like that... or someone who would spoil me as much as you spoil Senku."
Gen frowned. There was something about the tone... too sweet. Too intentional.
Senku replied curtly.
"I don't need to be pampered. Let's finish this." Luna didn't take the hint. Minutes later, while slowly doing her part, she persisted.
"Hey, Senku… do you have a girlfriend? Or a boyfriend, I don't know. I've never seen you with anyone. But a guy like you surely has someone drooling over you, right? If not, I volunteer, eh~" She laughed as if it were a joke, but her tone was playful, flirtatious.
Gen felt a pang in her chest. It wasn't exactly jealousy—he knew Senku didn't have eyes for anyone else—but hearing someone else flirt so blatantly with his boyfriend did provoke certain reactions.
From the other side of the door, Senku replied in a flat, almost bored voice.
"I don't have time for that. And no, thank you. I prefer to focus on work."
Luna let out a louder giggle.
"Oh, you're so cold... but I like that. Difficult guys are the most interesting."
Byakuya cleared his throat loudly from the kitchen.
"Luna, would you like more tea? Or better yet, why don't you finish that part and go home early? You have classes tomorrow."
Gen sat on the edge of Senku's bed, back straight, hands resting on his knees. The mattress creaked slightly under his weight. The room was dim; only faint light filtered in through the crack in the half-open door and the window with its partially drawn curtains. He could smell Senku's distinctive scent everywhere: the faint trace of chemical reagents, the neutral soap from the clean laundry, a hint of stale coffee in the mug he always left on his desk. It was a smell that, in recent months, had become synonymous with home for him.
Home.
That word hit him hard as he listened to the voices in the living room. Gen had never had a home like this. His childhood had been a parade of small apartments, moves due to his parents' jobs, quick dinners in front of the TV, and silences filled with forced laughter. His family were good people, but they had always been busy: double shifts, tours, rehearsals. Affection existed, but it was intermittent, like a magic trick that appears once and then disappears. There had never been a living room where someone made tea just because, nor a father who asked "How was your day?" with genuine curiosity, nor a space where he could sit in silence with someone who looked at him as if he were the most interesting thing in the world.
Until he arrived at this apartment, Ishigami.
Here, Byakuya greeted him with a pat on the back and a “The wizard has arrived!” that sounded like he was genuinely happy to see him. Here, Senku sat beside him on the sofa without needing an excuse, rested his head on his shoulder when he was tired from studying, and stole quick kisses when Byakuya went to the kitchen. Here there was laughter, silly arguments, and a constant warmth that Gen hadn't known he needed until he had it.
And now, from the other side of the door, a shrill, cloying voice was invading all of that.
“…and then the teacher said my analysis was the best in the class, but I told him, ‘No, no, Senku’s is much more insightful.’ You’re so talented! How do you manage to understand everything so quickly?”
Senku replied in his usual flat tone, the one he used when he wanted to end a conversation right away:
"I just read and think. It's not magic." Luna laughed as if she'd just told the joke of the year.
"Oh, how modest… I love that about you. You're so… authentic. Not like the other boys in the class who only talk about soccer or girls. You're different."
Gen gritted his teeth. He knew—with a certainty that needed no proof—that Senku wouldn't reciprocate that girl's feelings one bit. Senku was loyal to the core; if there was one thing he'd learned in these months, it was that when Senku decided someone was his, he meant it. He wouldn't betray him. He wouldn't hesitate. He wouldn't look the other way.
But that didn't ease the knot in his stomach.
Because Luna wasn't just flirting with Senku. She was encroaching on everything Gen had begun to consider his own.
"Mr. Ishigami, did you cook a lot for Senku when he was little? You really take care of him... How sweet. My mom's always working, so we hardly ever have home-cooked meals. I'm a little envious of Senku, having a dad who bakes cookies and everything..." Byakuya replied with his usual warmth, but Gen noticed the slightly strained tone, as if he were carefully choosing his words.
"I do what I can. Senku eats whatever I put in front of him; he's not very picky." Luna giggled again.
"Oh, how humble. I'm sure when he has a girlfriend or boyfriend, he'll be the best boyfriend in the world. He deserves someone who pampers him like you do... I'd sign up, eh~" Gen closed his eyes tightly.
There she was. The squeaky-faced girl didn't just want Senku. She wanted the whole package: the cool, intelligent boy who made her feel special, the warm apartment, the father who made tea and asked how she was, the quiet nights where no one yelled or rushed off to rehearsal. She wanted to be a part of that space Gen had begun to love with an intensity that surprised even him.
Gen ran a hand over his face, trying to calm the unease rising in his chest. He knew it was irrational. Luna was just a persistent teenager, nothing more. Senku would get rid of her as soon as he could. Byakuya wasn't stupid; he would have noticed the flirting by now and would be politely keeping the distance between his son and that girl.
But hearing how that girl interfered, how she praised Senku, how she flattered Byakuya, how she tried to fit into that family dynamic… it hurt him in a way he hadn't expected.
Because Gen had never had that. And now that he did, the thought of someone trying to steal it sent a cold chill through his stomach.
From the living room, Senku's voice cut through the air like a scalpel.
"Luna. Let's finish the job. I'm not in the mood for chatting."
There was a brief silence. Then Luna, her voice a little lower but still gentle:
"Okay… but someday you're going to have to relax a little, Senku. Life isn't all science and projects."
Forty eternal minutes passed. Finally, he heard the sound of chairs being moved, a backpack being closed, polite goodbyes. Byakuya, his voice firm but kind: "Take care when you get back, Luna. And thank you for the teamwork." Luna replied with, "Thank you, Mr. Ishigami! And tell Senku to let me know if he wants to study together again!" Footsteps toward the door. The door closing. Silence.
Gen exhaled slowly.
A few seconds later, the bedroom door opened carefully.
Senku entered, closed the door behind him, and leaned his back against the wood for a moment, as if he needed to compose himself. Then he looked at Gen, and his expression changed: from lingering grumpiness to something softer, warmer.
"You're early," he said, approaching with calm steps. "My old man brought you in here like you were a fugitive."
Gen didn't respond immediately. He simply got out of bed and, without a word, clung to Senku like a koala: arms around his neck, face buried in the hollow between his shoulder and collarbone, legs wrapped around Senku's waist. He weighed just enough that Senku had to hold him firmly, but not so much that he couldn't walk a couple of steps to the bed and plop down, still clinging to Gen.
Senku let out a low, surprised laugh.
"Hey… what's wrong?"
Gen didn't speak. He just tightened his embrace, inhaling Senku's familiar scent: soap, coffee, a chemical undertone that always calmed him. Several minutes passed like this: Senku rubbing his back in slow circles, Gen breathing against his neck without letting go.
Finally, Gen murmured against Senku's skin, his voice low and slightly husky:
"I heard everything. The way she flattered you. The way she talked to your dad. The way she said she envied what you have here… what we have here."
Senku sighed, but didn't let go.
"Luna is… intense. But it doesn't mean anything. You know that."
"I know," Gen whispered. "I know you won't let her in. I know you won't trade me for anyone. But… damn it, Senku. Hearing her try to interfere… in your house, with your family, in the place I come from and feel like I belong… it scared me. The fear of losing you, of losing this. I've never had a home like this. No one has ever waited for me with tea and cookies, or asked about my day like they really cared. And now that I have it… the idea of someone wanting to take it away from me really stirred something."
Senku stepped back just enough to look him in the eyes. His hands moved up to Gen's cheeks, holding them gently.
"They're not going to take this away from you," he said firmly, without hesitation. "Not Luna, not anyone. This place is ours. You've been a part of this for months. My dad loves you, I love you... and there's no room for anyone else trying to sneak in."
Gen swallowed. His eyes glistened slightly, but he didn't let the tears fall.
"Really?"
Senku nodded, his thumb brushing Gen's cheek.
"Really. I love you, a lot. More than I thought at first."
Gen let out a shaky laugh, resting his forehead against Senku's.
"I love you too, you idiot scientist. So much it hurts a little."
They stayed like that for a while longer: foreheads touching, breaths synchronized, hands intertwined. Senku kissed him slowly, unhurriedly, as if he wanted to seal each word. When they separated, Gen smiled slightly, still a little vulnerable but calmer.
"Sorry for the koala attack."
Senku huffed, but hugged him tighter.
"Don't apologize. I like it when you do that. Although I should train a bit so I can carry you properly..."
Gen closed his eyes, letting the words settle.
Yes. He was home.
And nobody was going to change that.