Aimdaqs

"No one ever helped me no matter how much I suffered. So, tell me...why would I help others if there's no benefit to it for me?"

After being sold off by his parents to human traffickers due to a physical deformity and ending up as a resident of the underworld, a jaded mercenary is killed during a mission gone wrong. 

"If only there was a way to carry my entire arsenal of weapons without weighing myself down..."

As he dies, he suddenly find himself waking up in a younger, unfamiliar body, in an unfamiliar world. He finds himself in a rundown orphanage located in a medieval world full of Magic and Monsters, his new body weak and frail. His new name is Jaedfern Meraled, or Jade for short. 

But he's not alone in being sent to this world...along with him for the ride is the Angel Arkiela, who was banished to this world for interfering with the human world out of boredom. Specifically, she used her powers to feed and amplify people's impulses and intrusive thoughts, including the people around Jade, whom she targeted to, in her words, "mess with", and subsequently went on to ruin his life.

She then claims that their lives are now intertwined...if one of them dies, so will the other. While being uncertain as to whether she's being honest about that or lying so that he can't afford to kill her, Jade can't exactly risk putting it to the test, so he errs on the side of caution. 

Grudgingly, he decides to accept her presence around him, having no other choice in the matter. With that settled, she reveals that when people are reincarnated with their memories intact, they're given OP powers, usually as a reward or consolation for their circumstances in their previous life, and she then checks what abilities he's been bestowed with.

In this world, there are three main elements to a person's Magic...their Magic Class; which is the core of their abilities, their Mana Pool; the quantity of Magical energy they possess, and finally, their Skills; special abilities that include active powers such as Appraisal and passive powers such as Heat Resistance. Each person possesses three Skills, without exception.

As for Jade, his Magic Class is...well, he doesn't have one. And his Mana Pool...is nonexistent, he possesses no Magical energy whatsoever. And finally, his Skills...he only has one, titled "Mercenary's Item Box", a dimensional storage power with a number of abilities that can be unlocked by Leveling Up the Skill.

Most people who are reincarnated are given OP powers, rewarded for either living a virtuous life, or as consolation for living a tortured life. But sometimes, people who've lived sinful lives, can be punished instead, bestowed with the bare minimum of abilities in worlds where such abilities are everything.
 And Jade is the latter. 

However, Jade may not necessarily be as bad off as it initially seems...because within his Item Box, is every weapon he owned during his previous life, weapons that don't exist in this world. Will it give him enough of an advantage to survive, and ideally thrive, in this medieval world rampant with violent crime and dangerous Monsters? One thing's for sure, it certainly won't be easy...

The Reincarnated Mercenary's Only Skill is Item Box

I raced across the space while firing out a barrage of bullets from a Phantom Copy of my assault rifle, grimacing as the bullets stopped right before they could hit the Elf and flew away, unable to penetrate the armor of intense, swirling wind surrounding him.

You've gotta be kidding me...he really stopped bullets with wind!? This is bullshit...

He then leapt straight towards me, driving his fist towards my head as he closed in on me in an instant.

I reacted as fast as I could and quickly ducked under his punch, a couple of small cuts appearing across my face as the swirling wind around his arm grazed my skin, before I sprang back as I unleashed a Phantom Copy of a Destruction Magic Spell I'd got from Arkiela, opening a portal right above my opponent, the beam blasting down from it.

Chapter 79 - The Order of the Black Rose: Postlude(Part 7)