Welcome to My Mansion
Tap, tap, tap.
Homeroom teacher, grade-level deputy, and math instructor Yamamoto Baki wielded the chalk with swift precision. His forearms—nicknamed the Murder Tank for their brutally rippling muscles—contrasted sharply with the dainty, almost girlish script blooming across the blackboard.
"Differentiation is the English term's translation, coined from the idea that points and lines, lines and planes, planes and solids share relations akin to those in calculus."
"In other words, when you slice a solid into infinite layers, each infinitesimal slice is called a 'differential'—that's the etymology..."
But seriously, who knew chalk could produce handwriting this cute?! The awe fades fast when you glance at the musclebound uncle beside it. Maybe that's the downside—immersion shattered. What a tragic divine prank, pairing such mismatched talents.
'Or is it a gap moe jackpot?'
Who knows the commercial value of the Murder Tank's charm points, but as a math teacher, Baki was solid. He explained things in ways even dense students could grasp. That gravelly voice of his carried a chilling magic that gripped the soul.
"You there—stop daydreaming and look up front."
"...Y-Yes, sir!"
Math class naturally had the most dropouts, so plenty spaced out. At first, fear of murder kept everyone on edge, but once they realized survival was guaranteed, focus waned. Even in third period, Kenichi kept sneaking peeks at me—he was firmly in the 'gave up on math' club.
"Tsk, tsk. Daydreaming in class? Quite the delinquent, aren't you."
"...You're the one doodling in your notebook since earlier."
Busted. My desk mate, Sawamura Cento, who'd been front-row to my fantasy drawing show, called me out. She scowled at my three-dimensional sketch of the Murder Tank.
I deflected. "Nah, I'm different. I've already mastered the whole lesson perfectly. Flawless!"
Before entering this game, I was a STEM student from hyper-competitive Korean high schools. Not top-tier grades, but always upper mid-pack—enough for an engineering college. High school memories blurred, but calculus? Piece of cake.
"...You sure talk a big game."
Cento, my partner through thick and thin, knew my brainpower by now and dropped it. She just clicked her tongue and faced forward. A peek at her notebook: crammed with full solutions, despite knowing it all. Model student.
Anyone could see it—teachers adored her. To wear a mask forever, that level of effort was mandatory. She'd zone out all day, and they'd just think, 'Off day, huh?'
Me? Perpetual sly grin, spacing out, but nailing questions when called. Never caught slacking, so I sported the honors badge. Worlds apart from Kenichi, who ogled me obviously from the front row.
Dude, no fear of backlash?
Right on cue, Baki finished the board problem and spotted Kenichi's glances.
"Kitagawa Kenichi."
"...Huh? Y-Yes?"
"Front and center. Solve number five."
"...Ah."
Kenichi slumped to his doom. Inevitable execution. Well, verbal lashing from the Murder Tank beat actual death.
Way better.
Chin in hand, I watched him tremble through the solution, mulling my plans.
'I got greedy, so time to own it.'
Worst case, solo survival. But the path was set. My mere existence had triggered butterflies. Originally, minimal interference—just nudging episodes. Now? Intensive training for key players.
To save them? Nah, to save myself.
Early episodes' bad ends just killed the hero, Kenichi. Mid-game? World ends. Survival options needed multiplying.
First target: desk mate, Sawamura Cento.
"Kenichi! What the hell were you even listening to?!"
I tuned out the thunderous roar as white noise, refining my blueprint.
***
After classes, Cento shouldered her bag, waiting for Ichimaru Shiki. Cleaning duty, apparently. She'd ditched library committee for his whim—infuriating.
"Late ass."
Stone-faced, she stared down the stairwell.
"Peekaboo."
Somehow, right beside her. Shoes changed, too—what trickery? Shiki shrugged with his usual sly grin.
"Ah, kept you waiting? Sorry. Kenichi got kidnapped by Murder Tank sensei—cleaning took forever..."
"Spare me."
Predictable excuses. Cento shrugged unconsciously, blunt. "Just hurry up. To your place."
"Ho ho."
Shiki's grin irked her again as he led on. House far from Karakura High in Minato Ward? Train station bound.
"Haha, prices here are insane. Gotta head outskirts."
Fair—unless lotto jackpot like him, Tokyo core was brutal.
'Even post-bubble, wild.'
She nodded silently, boarding with him. Long wait ahead—
"Our stop!"
"...?"
Cento furrowed her brow. Shinagawa Ward, one down from central. Bustling after Shibuya and Minato. Tempted to snap, but she swallowed it—just a twitch.
No point bickering; she'd lose IQ points.
"Almost there! Hang in, partner! Fighting!"
Enduring his moronic cheers, they reached a dingy alley. Far from student pads—prime for shady deeds, deserted.
"...You."
Bad life flashbacks hit: Planning to kill me?!
Regretting her lapse, Cento surged aura. Fight to the end.
Shiki waved innocently. "Whoa, wait! We're here—properly. Bear with me."
He strode in, calling brightly. "No clue who's on duty, but could you open up? It's Shiki—your mooching regular for months."
...What?
Cento scowled, watching. Sharp mind guessed sorcery, post-yesterday's wild tale. But...
'Said it was his house?'
That pathetic begging? Maybe low-rank in some org.
As she pondered, Shiki quipped, "Thanks for opening!"
The scene flipped.
"...Huh?"
Gloomy alley vanished; grand estate gates and stone walls appeared. Edo-period drama scale—unreal for urban Tokyo.
'...Barrier?'
Expected something, but stunning. Cento froze, blinking.
Shiki marched to the gate undeterred. Knock—creak, it opened.
"I'm home."
Through the gap: uniformed retainers. Dozens, eyes on the squinting man.
Cento, overwhelmed, hung back.
Shiki crossed with sly smile.
—Master Ichimaru Shiki!
Thunderous chorus shook the air. He sauntered through like it was normal. Servants bowing en masse—Red Sea part two.
—Welcome home!!!
Or Messiah vibes.
'...What the hell?'
Still dazed, Shiki spun, shrugging at her. "Sorry, greetings are over-the-top."
"...A bit?"
"Embarrassing, but guest status—no fixing it. Bear with! Anyway, welcome!"
Amid the crowd, Shiki bowed theatrically, sly grin intact.
"Do come in—to my mansion."
Perfectly fitting scene.