Deadly Questions

Me, Mikan, Zack, and the rest of the raid members stared at the quest glowing before us. It wasn’t just any quest. It was a trial that could end all of us. One wrong answer, and we would all die here.

The players and even the NPC raid members looked shaken. Mikan and Zack were no different.

“This is so sudden… This floor used to only have traps and puzzles that weren’t too hard to solve. But this quest… this one’s designed to crush us!” Mikan’s voice was tight with seriousness.

“WE’RE SCREWED! I’m no good at calculations, puzzles, or riddles… this is the end for me.” Zack slumped, his face pale.

“How can an engineer like you be bad at math? That’s ridiculous,” I snapped at him.

“I’m not lying! When I build weapons or machines, it just pops into my head like—BAM! BOOM! SHINGGG!” Zack flailed his arms dramatically.

I sighed. This man was beyond understanding.

“Kyouze… I’ll try my best to help with this quest! Back in middle school, I was second place in the math olympiad!” Mikan clenched her fists, clearly trying to be useful.

I gave her a small nod and smile.

Suddenly, the quest interface lit up before us.

[THE QUEST WILL NOW BEGIN!]

[YOU MAY WORK TOGETHER TO SOLVE THE QUESTIONS OR PUZZLES THAT WILL APPEAR!]

[IF NO ONE SUBMITS THE CORRECT ANSWER WITHIN THE TIME LIMIT, ALL TRAPS AND MONSTERS IN THIS FLOOR WILL ATTACK UNTIL YOU ARE WIPED OUT!!!]

Reading the warning only tightened the knot in our stomachs. Panic began to spread.

Mikan and Zack quickly braced themselves.

[QUEST: MATRIX OF DEATH HAS BEGUN!]
[FIRST QUESTION: MULTIPLE LAYERS OF MATRIX! YOU HAVE 40 SECONDS TO ANSWER OR DIE!]

Question:
You are given a block matrix

F=[A0​IA​],A=[20​12​]

where I is the 2×2 identity matrix and 0 is the 2×2 zero matrix.

Find the determinant of F!!!

As the problem appeared, a glowing menu opened in front of us where we could type our answers. Everyone scrambled to calculate, hands shaking. Zack clenched his head, furious.

“Damn it, this is insane! And only forty seconds?! This isn’t fair!” He slammed his fist to the ground.

“Shut up, Zack! I’m calculating!” Mikan snapped, her brow furrowed.

Twenty seconds ticked by. Many players submitted answers, only for their screens to flash red. Wrong.

Ten seconds left. Mikan submitted hers. She looked confident—but the moment she pressed submit, her screen turned red. Wrong again.

“No way…” Her face fell into despair.

Five seconds remained. Everyone else had given up. But not me. From the moment the question appeared, I already knew the answer.

I calmly submitted:
[Answer: 16]

[…Checking answer…]
[CORRECT! CONGRATULATIONS. PREPARE FOR THE NEXT QUESTION!]

The raid’s morale skyrocketed at once. Mikan looked at me in shock, as though she couldn’t even imagine the answer.

“Kyouze… how did you solve that so fast?” she asked, eyes wide.

“Huh? Sixteen? That makes no sense… how the hell did you do it?” Zack still looked doubtful.

I sighed, then typed out my reasoning:

[For a block triangular matrix, det(F) = det(A) × det(A).
det(A) = (2×2 − 0×1) = 4.
So det(F) = 4×4 = 16.]

“Understand now, Zack?” I asked flatly.

“Sorry, Kyouze… I don’t get any of this.” Zack scowled.

“I figured as much. Not surprised,” I teased lightly.

Mikan whispered, almost in awe. “Incredible… are you some kind of genius?”

Her words stirred a memory. Back in school, I had loved studying—especially mathematics. My teachers had even nicknamed me the Quantitative King.

“No… I’m just skilled in this field,” I answered casually.

The raid cheered and praised me. For them, I was their savior.

The system wasted no time.

[SECOND QUESTION: ADVANCED DEATH MATRIX. YOU HAVE 30 SECONDS TO ANSWER!]

Question:
Consider the matrix

K=​2100​0210​0021​0002​​

(a) What type of matrix is this (upper, lower, diagonal, etc.)?
(b) Find det(K).
(c) Without full calculation, state whether all eigenvalues are the same or different.

In less than two minutes, I had submitted:

[ANSWER:
(a) Lower-triangular (all nonzero entries are on or below diagonal).
(b) det(K) = product of diagonals = 2×2×2×2 = 16.
(c) All eigenvalues = 2 (since it’s triangular with diagonal entries = 2).]

[CORRECT!!!]

“WHAAAA AMAZING KYOUZE! YOU REALLY ARE A GENIUS!” Zack shouted, while the raid roared in excitement.

I continued, solving question after question with ease. Within minutes, we reached the fifth and final challenge.

[FINAL QUESTION: MATRIX OF OBLIVION!]
[YOU HAVE 10 MINUTES TO ANSWER!]

Question:
You are given the Matrix of Oblivion

M=​105​216​34k​​

Find the determinant of M in terms of k.

Determine the values of k for which M is not invertible.

For k=−1, compute the eigenvalues of M.

If all raid members must align their EtherCode frequencies to the trace of M, what is the synchronization value (the trace)?

While the raid panicked and scribbled frantically, I finished the solution in five minutes.

Calmly, I entered:

det(M) = k + 1

Not invertible if k = -1

Eigenvalues (k = -1): 2, (1 ± i√7)/2

Trace (k = -1): 1

[CORRECT ANSWER!!!]

[CONGRATULATIONS! YOU HAVE CLEARED MATRIX OF DEATH!!!]

[THE FLOOR TRANSFORMS! THE PATH TO THE DUNGEON BOSS IS NOW OPEN!!]

The dungeon shifted before us, the traps and monsters instantly disappeared and the floor forming a direct path ahead, like a crimson carpet rolled out for us.

We rushed forward.

“WAHAHAHA THIS IS TOO EASY! YOU’RE AMAZING, BROTHER!” Zack slapped my back proudly.

“I’m not your brother. Shut up and move,” I said coldly, but Zack only laughed harder.

Mikan scolded him, telling him to stay serious. Then she looked at me. “Um… Kyouze… you solved every single question on your own. You really are a genius. I didn’t expect that.”

“It’s nothing. Other than gaming, the only thing I’m good at is math…” I said quietly, my mind drifting to memories of my late grandfather who taught me mathematics. He had been a mathematician in his youth, and he always smiled when teaching me. That smile had given me this gift.

Before I could dwell further, we reached the end of Floor Five.

Mikan activated her [Personal Netherbyte GPS]. The signal flickered, showing the positions of the five Player Faction Leaders trapped on Floor Six.

“Kyouze… this is bad! I can see the Eclipse Reign, Lunaris Vale, Machina Legion, Nihilwalker, and Scarlett Sanctum leaders… they’re at the far end of Floor Six. Their signals are flickering… which means they’re fighting the Floor Six Boss… and they’re dying.”

Her words froze my mind. I imagined Ayane, leading Scarlett Sanctum bravely, now cornered and near death.

I clenched my fists. I couldn’t waste another second.

“Mikan, Zack, everyone! We’re defeating this boss now and rushing to save them!”

“YES!!!” all 498 raid members roared with me as we charged forward.

The moment we stepped into the arena, we were greeted by a towering figure. A white-haired demon with glowing red eyes. His face half-hidden behind a crimson grid of matrices. He wore a red-black suit patterned with shifting equations, a crimson old-style hat resting on his head. Black horns, wings, and pointed ears left no doubt.

This was no hologram.

A notification appeared:

[FLOOR 5 BOSS HAS APPEARED!]

[YOU ARE NOW FIGHTING A BOSS!]

《GRIDEON, THE DEMON OF THE INFINITE MATRIX》

[BOSS LEVEL 7]

“Well, well… I didn’t think you’d survive my riddles so quickly. Perhaps I’ll just create even harder ones, kuhahaha…” Grideon’s murderous intent filled the air.

The raid trembled with fear. Everyone except me.

I leveled my sword at him. “We’re in a hurry. To hell with your mediocre riddles. I’ll defeat you right now!”

My time was limited. I would use one of my hidden cards.

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