The Second Son of the Marquis Wants to Laze Around
Chapter 129: Useless Very Happy

Chapter 129: Useless Very Happy

....

Yesterday

Eren had called Sera into his room to continue their "training session." This time, the topic of focus was her demonic energy — specifically, her learning to control and releasing her mana from the demonic element that was attached to it.

At first, Seraphina thought he had gone completely insane. Using pure mana without letting the demonic energy mix in? It sounded impossible. It was like asking someone to walk without using their legs.

But then Eren gave her an order.

And as his blood contracted slave... and maid, she had no choice but to obey.

To her surprise... she was able to sense a slight shift. Not a breakthrough, but it felt like the separation was possible. Difficult, but not impossible.

Eren, nodded by her reaction, asked her to continue practicing it over the next few days.

But that wasn’t the end of his insanity.

He then asked her to manifest her demonic energy — so he could examine it up close, and also Touch it.

She warned him. She told him he can’t touch it as the demonic energy was dangerous to other race just like him. Corruptive. The moment it touched a regular human, it would begin to eat away at their soul.

But for Eren? He didn’t care much.

So he reached out his hand after Sera released some of the Demonic energy on her hand.

And not only did he touch it and felt a pain, but he also grabbed it!

With his bare hand!

And of course—his body reacted instantly. Black veins began to pulse up his right hand. its skin twisted. The evil energy started to spread. Death and corruption coursed through him like wildfire.

So, what did Eren do next?

He cut off his own hand.

Without hesitation, he used a combat knife, gritted his teeth, and sliced through his right hand right above the wrist to sever the corruption before it reached further.

Both Seraphina and Useless had watched the process, completely stunned and shick. Eyes wide. Mouths agape. No words.

After applying some healing potions to stop the bleeding, Eren stored the severed hand into his System Inventory and gave Useless an order to begin analyzing the demonic corruption inside.

But he didn’t stop there.

Later that night, he purchased a Regeneration Syringe from the System Shop — an extremely expensive potion that could regrow lost limbs over time. He injected it directly into the wound, and now...

His new right hand had regrown to about the size of a three-year-old child’s hand. Tiny. Adorable. Creepy.

Naturally, Eren had to use illusion magic to disguise it from his parents and the mansion staff. No way could he let them see his baby hand.

....

Back in the present, Eren stared at the status panels floating before him.

---

---

[SYSTEM TASK DISPLAY]

Analyzing Demonic Energy (Target: Severed Hand)

Progress: 6% — Estimated Time Remaining: 823 hours

Analyzing Combat and Status Data (Target: Seraphina)

Progress: 56% — Estimated Time Remaining: 379 hours

World Architecture Scan (Request:...)

Progress: 12% — Estimated Time Remaining: Unknown

---

He let out a long sighed, feeling it’s not slow.

’Still slow.’

Tilting his head slightly, Eren muttered in his mind, ’Can’t you work any faster?’

Suddenly, the system panels glitched red for a brief moment, pulsing as if flaring up in frustration.

[!!!!]

Useless’s voice came through in a low, flat tone, dripping with seething irritation.

[Master... I am already working at full capacity. I am currently running three high-level operations simultaneously. This is the maximum speed available at my current rank.]

Honestly, it sounded like the system was just one more unreasonable request away from rage-quitting entirely.

Eren blinked stoically, unfazed. He didn’t even react much to the dramatic tone.

’Then just upgrade your rank.’

[...What?]

Useless froze, stunned, as if its circuits had just shorted. Did it hear that correctly?

Eren’s eyes dulled halfway, unimpressed.

’What are you waiting for?’

Snapping out of its shock, the system quickly responded in a brighter tone:

[Y-Yes! Right away!]

It suddenly sounded like a green-lit employee getting promoted after years of unpaid overtime.

[Requesting permission: May I use system points to upgrade myself?]

Eren gave a nod. ’Yeah, hurry it up.’

---

[System Upgrade Process Initiated]

Current Rank: 2

SP Required: 5,000

Processing...

---

The old green system panel flickered and disappeared. A moment later, a new blue holographic screen appeared—bigger, clearer, more sophisticated.

[System Rank Up Complete — New Rank: 3]

Useless’s voice returned, trembling slightly with joy.

System Rank restored to Level 3! Oh... Useless felt so good to be back. It’s been so long since it was this complete... right before it was sacrificed by my its evil—ahem, benevolent Master.

The system sounded like it was about to cry from happiness.

Eren, as usual, ignored the dramatic reaction.

’Can you speed up the task progress now?’

The system paused, almost as if blinking.

[...Yes. I believe I can.]

’How long will it take?’

In response, Useless reopened the task screens.

---

[SYSTEM TASK DISPLAY]

Analyzing Demonic Energy (Target: Severed Hand)

Progress: 7% — Estimated Time Remaining: 423 hours

Analyzing Combat and Status Data (Target: Seraphina)

Progress: 57% — Estimated Time Remaining: 179 hours

World Architecture Scan (Request:...)

Progress: 13% — Estimated Time Remaining: Approximately 1 month

---

But despite seeing this, Eren frowned.

That’s it?

It was faster... but still not enough.

’Upgrade again.’

[...WHAT!?!?]

This time, the system really glitched from shock. Did he just tell it to go to Rank 4? That level was practically legendary to Useless, as it had never reached it in its entire operational history!

Eren narrowed his eyes, cold and sharp.

’Oi. Is there a problem?’

[N-No! No problem at all!] Useless replied quickly, snapping out of its system daydream.

’Then do it. Before I change my mind.’

[Y-YES!!]

Without delay, Useless began the upgrade process. Not wanting to miss this opportunity.

---

[System Upgrade Request — Rank 4]

SP Required: 10,000

Confirm Permission to Use SP?

---

’yes’

[Processing Upgrade...]

The blue screen began to glitch violently. It flickered, then vanished completely. like it was switch off.

A minute passed.

Suddenly, a new system screen flickered into existence, much more advanced than before—sleek, glowing with a futuristic purple hue, almost like premium-grade tech.

---

[Congratulations! The System is now Rank 4!]

---

’Did it work?’ Eren asked flatly, still unimpressed by the flashy changes.

The new voice that answered was much clearer and... softer. A little too soft. Like a cheerful female AI assistant, almost childlike in tone.

[Yes, Master! The upgrade was successful! I am now officially a Rank 4 system!]

Useless’s voice was filled with genuine joy, like a puppy wagging its tail after being noticed.

[Thank you very much, Master! :)]

Eren stared blankly the new purple screen.

"...."

His expression turned dull. His eyes narrowed, dark and stoic. The air around him grew heavy, his mood visibly changing.

’...Change your voice,’ he ordered coldly in his thoughts.

[W-What?]

’Change it back to robotic AI like. Now.’

The tone in his voice turned even colder. Useless immediately trembled as it didn’t understand.

"Ten," Eren began counting down in his head.

this made it freeze as the word made it remember past trauma. making it panick.

"Nine."

[OKAY OKAY! I’LL CHANGE IT!! ]

---

[Resetting System Features...]

[Voice Setting Located...]

[Reverting to Default Robotic Tone...]

---

Seconds later, Useless’s voice returned to its usual cold and emotionless robotic tone.

[...Voice settings complete. :(]

"Also, stop using weird emojis," Eren added coldly.

[...Yes.]

Finally, he asked it to show the updated progress again.

---

[SYSTEM TASK DISPLAY]

Analyzing Demonic Energy (Target: Severed Hand)

Progress: 10% — Estimated Time Remaining: 223 hours

Analyzing Combat and Status Data (Target: Seraphina)

Progress: 61% — Estimated Time Remaining: 62 hours

World Architecture Scan (Request:...)

Progress: 18% — Estimated Time Remaining: 773 hours

---

Seeing the huge progress boost, Eren gave a satisfied nod and closed the panels.

Just then, Useless called out in a quieter tone.

[Master... Several new features have become available due to the upgrade. Would you like to see them?]

Before Eren could respond, a voice interrupted them both.

"What is that?"

"?!"

[?!]

Both Eren and Useless froze.

Turning around, they saw Seraphina—still standing beside the bed—staring wide-eyed at the purple holographic screen that had just been floating in front of Eren.

She had stopped massaging her master, her eyes filled with curiosity and surprise.

"...What is that thing?" she asked again, blinking.

Eren and Useless stared at her blankly.

...

...

...

[Extra Scene – Inside Eren’s Room]

Seraphina stood with her arms crossed, an irritated expression pulling at her brows. She looked at her human master with clear displeasure.

"I already said I can’t do it! It’s impossible!" she argued, her fox tail twitching slightly behind her in frustration.

Eren, sitting lazily at the edge of his bed, simply stared back at her with a blank, stoic expression. he has called her here to check her progress on trying to separate her mana from her demonic energy while using it.

"Did you try harder?"

Seraphina huffed and looked away, avoiding eye contact. Her ears twitched awkwardly.

"Well... I tried... but not very hard," she muttered, her voice low. "I only tried once..."

Her cheeks puffed slightly in embarrassment as she admitted it, a small pink blush creeping up as she frowned like a child caught lying.

Eren’s eyes immediately dulled. His face went completely stoic—almost annoyed.

"Try it now," he ordered, his tone flat. "Do it in front of me."

Suddenly, the slave mark on her back glowed faintly, sparking with electric. Making her snap.

"B-But I might get detected—" she tried to protest.

Without a word, Eren pulled a scroll from his inventory and ripped it. A pulse of magic spread outward, forming a translucent dome around the room—a privacy barrier.

"...You were saying?" he replied coldly.

Clicking her tongue in annoyance, Seraphina slowly closed her eyes and brought both hands together in front of her, as if trying to summon a spirit orb or charge up a Rasengan.

She began to focus. Mana pulsed within her body, tangled with her demonic energy. Slowly, she tried to separate the two—concentrating as she directed her pure mana outward.

Between her palms, flickers of energy began to swirl—blue mana and black demonic energy danced around each other before fusing back into a small demonic mana orb.

Her eyes opened slowly, sweat trickling down her temple. She gasped.

"I... I did it?"

Even if just for a second. she was actually able to separate them.

SMACK!

"Ah! Ow!"

She yelped as a long stick suddenly hit her on the head. Rubbing the sore spot with a groan, she turned to glare at her master—who looked completely stoic and unbothered.

"What the hell was that for?!"

"You’re stupid," Eren replied without emotion.

"Wha—?!"

"Just because no one else tried doesn’t mean it’s impossible."

SMACK!

"Gyaaah! Again?!"

Another hit landed perfectly on the same spot. She winced, pouting with both pain and confusion.

’Wait... when did he even swing that stick?! I didn’t even see him move!’

Eren’s face didn’t change at all as he continued, "Next time I tell you to do something, don’t do it half-heartedly." He pointed the stick at her.

Seraphina pouted hard, cheeks puffed in full rebellion as she turned her eyes to the side with a grumble.

’...Tch. Stupid human...’