2050, the Earth…

My name is Yuusha, which just translates to "hero". I am a freelancer, mainly doing in engineering and technical work such as fixing electronic devices of households. Sometimes I accept projects and commissions. I have a deep passion in science, and dream to do something big for this world using my knowledge. But the dream seems very far away. I am twenty-three years old this year.

And to be honest, I am completely blind when talking about my future. Although I want to do something big, I do not know where to start. I do not even know what the world needs, because there are probably someone out there having the same idea as mine, started doing it already. But that is at least what I am thinking as of now. That day has changed my life forever.

- Delivery!

Maybe my relatives or my friends send me a package, because I have no recollection of ordering something online. I receive the package and sign the confirmation paper, then bring it into my living room. I use a photon knife to cut the cardboard box, and under layers and layers of styrofoam and bubble wrap, there is a tablet. It is as thin as a glass sheet, and I think that it is not something from this present era.

I check the box, but the only information I see is my house address, and the sender part says that the package is from 2100. Yes, in 2040, delivery through space and time has been enabled with the revolution in special relativity technology, and one can send a package to the past of the future. However, who would send me a package?

I take the tablet out of the box and inspect it. There is a power button, so I turn it on. The tablet screen shows the loading screen, and after some kind of compiling information, a hologram of a young, female scientist appears.

- This following message is a confidential one, so please make sure that if you are the receiver of this package, you are the only person to know about this.

This is becoming scary. I flickered my hand to signal to close all windows and doors and continue hearing the message.

- Hi there, my name is Mirai, and I am a scientist from 2100. Now, listen closely to this. In 2100, the Earth will be dominated by an alien species called the Intruders. So, in short, what is happening now is that this package is sent to 2050 as a warning, also as a help to humanity to prepare for such chaos.

Everything is going off the track from this point after I hear such warnings. I know that I want to do something for the world, but this seems a bit overwhelming to absorb.

- Basically, you would have a 50-year period to prepare to fight the final war in 2100, so of course I would be helping you in this journey. But first, from this tablet, access the arsenal. This is a collection of human weapons from all time, at least until 2100. Tap on the submachine gun called SMG01 to summon it.

Although I am still suspicious of everything, and a bit scared, but I still do like Mirai said. A beam of light shines on my hands, and a submachine gun appears out of nowhere. It looks more like a laser gun that kids usually play.

- Yes, this is your first weapon, the submachine gun SMG01. Intruders cannot be killed with material projectiles due to their very hard shells, so we need to penetrate their shells to break their core, which is somewhere in their head, or their upper chest, depends. This will be your friend for quite a long time, so please be familiar with holding it.

I inspect the gun, and it seems that there are no major differences between today's weapon technology. Moreover, it is lightweight and quite small in size, so I can carry it with me.

- Now, they are heading this way. Get ready for your first battle. – The tablet says.

- Who are heading this way? – I ask.

- The Intruders.

Suddenly, my door breaks down, and two ugly creatures with weapons came in. In the fear, my hands unknowingly direct the submachine gun at the Intruders, and my pointer finger presses the trigger before I even realise. A powerful laser beam emits from the barrel, pierces through the Intruder, and makes it immobile. The next moment, my gun is already aimed at the second Intruder and makes it collapse with a second shot. I am still trying to regain my consciousness.

- This is the aim assist function of the gun, which I have equipped to other weapons in the arsenal for you also. All that is needed is for a person to wield it.

So that is not my instinct at all. I should have not been expecting much from myself, an amateur in such gun issues.

- By the way, we are not done with the issues. Now, I need you to hold for some time. The Intruders in 2100 should have sent its army back to 2050 to kill you, the person ruining their invasion plan.

To be honest, I do not even need her to tell me that. Faraway, I see some black dots on the sky approaching me. I quickly glance at the arsenal and take out a mounted plasma launcher. They are coming in planes, so why not?

Suddenly, there are many more black dots on the sky. I lock the targets and press the trigger. A burning plasma ray penetrates the atmosphere and vaporises every plane on its path. Seems like everything will be okay. I continue locking on other targets and knock down quite a number of them, but then the planes just continue approaching.

They start firing lasers missiles at my direction, and I have no choice but to redirect my plasma launcher to destroy them first. The planes keep coming, so close, very, very close. What to do now?

In just a tick, I cannot keep up with the shooting, and I feel the heat of a missile touching my skin…

Goodbye.

Wait, I am still alive. What happened? The planes disappear, and I am unscathed.

- Congrats on your first trial. The disappearance of the planes signals that the humanity has been saved from the Intruders. However, this also means that we need to be very cautious in every of our move, to make this come true. Now, let me guide you through the use of the Codex.

The screen automatically switches to the arsenal, and some of the words are highlighted. Then, the holograms of highlighted items appear one by one.

- As you can see, our arsenal consists of three main functions: offensive, defensive and support items. Simple as it is, offensive items deal damage to the Intruders, such as armaments. Defensive items protect you from the Intruders, such as barriers and shields. Support items aid you when you wield the offensive items, such as tactical throwables, trackers, EMP device and UAVs. For example, when facing an Intruder holding a machine, use the EMP device to disable the machine, then use throwables to distract and a gun to finish him off. – Mirai instructs me with the basic of the tablet.

Then, the tablet switches to the Intruders encyclopedia part. The information of Intruder types and what event would happen at what time is clearly stated here.

- So that is all for today. I hope you can remember this information as soon as possible. We will be departing for our first missions soon. But before that…

- Yes?

- Staying in this tablet is a bit uncomfortable for me, so I would like you to assemble a physical shell for me to stay in. You are an engineer, so I do not have many worries, but I will still instruct you on how to do so. It would take some time to assemble, so you can get rest for today.

Oh… A physical version of Mirai… Yep, definitely benefit from it.

I do all the personal hygiene and go to bed. Of course, I am having the tablet with me now to read through the encyclopedia again.

Sure enough, reading something is a perfect way to make yourself asleep at lightspeed, and I am already sleeping, holding the tablet with the screen still turned on, without myself even noticing…

The next morning comes, and yes.

- Yes, you connect these two wires together to link the battery with this motor. Solder these parts together and link to the control panel in the right arm. Yes, correct…

- Ok, so we have this right arm done. Let me try it out a bit to see if it is working.

I am currently assembling the components to make a body for Mirai. She says that everything is in the arsenal, but then why am I doing everything from scratch? What a pain.

I continue to spend the whole day to finish making other body parts, then connect them together and test run to ensure stability and other factors. After a few tries, the machinery part is done, and I use the some human-skin-like material to cover the physical body, aesthetic purposes mainly. For the last part, I let Mirai upload her data on the control system of the physical body, including the arsenal and Intruder encyclopedia. Now, she can also summon items and inform me about Intruders whenever I forget.

After the upload, the physical body started to move its fingers, then its hands, limbs, and finally the body. Even I feel impressed with the masterpiece I have built. But then…

- Thanks for making this physical body for me. Nothing more to expect from a freelancer engineer. I really appreciate your efforts, and I know that you are quite asleep now, but can you build a portable solar battery for me also? The instructions are in the tablet.

- Fine…

And I spend the rest of the night to design a solar battery. It will be placed on Mirai's back, near the control system in her head.

Working an 18-hour shift is a nightmare for a freelancer like me who can freely choose when to work, and this drains all of my energy. I get on the bed as soon as I attach the battery onto Mirai's back. While lying on the bed, I just think that now, I am technically having a robot assistant, which resembles a beautiful girl, and topped with future knowledge and skills, and anything that would make a normal boss feels envious, and any human assistant cries in shame.