"Kenny! Wake up! You have to go to school!"

Listening to my neighbor across the hall yelling at her son every morning had been my daily routine for the past few weeks since I moved here. This flat was new, so there weren't many occupants yet here. And I liked it better that way. It was quiet there. Except for that sound of the mother waking up her son every morning.

Everything seemed perfect for me living my daily life, until one day, a strange thing happened. I woke up in the morning, and I found my furniture was moved from its original place. "Did I sleepwalking and move the furniture during my sleep?", that was the only thought I had in mind. "What? Did I even sleepeating too?", I thought after I open my fridge to find some foods also missing.

Or, that was all I thought at first.

It might actually look like I was sleepwalking, if not because of what I noticed one day. It was not just my furniture that moved. It was also where and how I place my things. I'm an OCD, and I organized my things based on alphabets. However, that day, I found my things being placed disorganized. And there was also a trace that someone else had used it.

I couldn't help but started to think that there was someone else living, hiding, in my flat.

So I started searching every place that could be a hiding place for humans. Be it a child, or an adult. But it turned out nothing.

The event had been happening for about three days, and then something weird happened at one morning when I looked at the bathroom's mirror. There was something written on it using a marker: "Get out of my house!"

"What the hell?! This is my house, not yours!", I screamed. I began to search the flat thoroughly. He claimed the flat as his house, so, whoever this intruder was, he must still be here. And yet, the result still nothing. Not even a trace of other person living in my flat except the fact that some of my things were moved, and there was that message on the bathroom's mirror.

So I did the only thing I could do at the moment. Wrote a reply to the invisible intruder using his method, by writing the message on the mirror. Which he replied again the next morning. So on for next few days.

"This is my house! You get out!"

"Who are you? Show yourself!"

"Show myself? You're the one who's hiding! I'm not! I've been living here for a few weeks."

"Wait! Wait! I'm not hiding either! I've been living in this flat for a few weeks myself."

That was the last message from the invisible intruder, who claimed the same position as I did. Something strange had happened. It looked like there were two persons, living in one, same flat, but never saw each other. "A portal to alternate universe" scenario came to my mind, but hell, that was way too science-fiction. There should be any other explanation that made more sense to the situation. Or maybe not? Maybe it was actually a case of alternate universe.

Then I had an idea. Asking the intruder to meet up sounded like the best idea at the moment, so I planned to write him another message to meet up. Just when I was about to write the message, I heard knocks on my door.

I walked to my front door and opened it. I saw two men in leather jackets stood in front of my door.

"Billy Drake?", one man asked. The expression on his face looked like he wasn't sure who he was looking for.

"Sorry. Wrong address", I replied. And when I was about to close my door, the man held it and opened it back. And then, he asked me again, this time with a smile of certainty on his face, "Daniel Elbaff?"

That surely surprised and confused me. The first time, he mentioned a name I never heard of with uncertainty, and then he mentioned my name with certainty.

"Who are you?", I asked. Before I could do anything, the man struck me with a stun gun, and I passed out.

Upon waking, I looked around, and I realized that I wasn't in my flat anymore. I was in a four-walls room, painted in white, with nothing in it, except a bed where I was tied onto. I didn't waste my time thinking of who those men were, or where I was, or why I was brought there. All I did was trying to release myself from the bed.

"Hi, Daniel. There's nothing you should worry about. Everything is completely fine. Please just relax", a voice that came out of a loudspeaker stopped me.

"Hey! Who are you? What are you doing to me? Let me go!", I yelled.

"Oh, don't worry. We will. Right after we're done with the reboot", the voice told me again.

"Reboot? What are you rebooting? And why am I tied in here?", I asked.

"We are rebooting you", the voice answered. And then he added, "Well, there was a troubleshoot happened, so you lost some of your memories while you were here before. I guess you deserve a bit of explanation".

Despite my situation, the voice sounded calm and soothing. I didn't feel any threats out of it, so I started to relax, and listen to what the voice was going to tell me. The belt tied me really tight to the bed, though. There was nothing I could do about it. However, it seemed like I had been in the room before, according to his explanation earlier.

When they saw me lay back and relax, the voice started his explanation.

"First thing first, you're the one who volunteered to be here", the voice said. "We are in a government military research facility, and we are conducting an experiment. On you", he explained.

"I volunteered? I didn't even remember", I responded.

"Well, as I said. There were a troubleshoot happened, and you lost some of your memories. And we didn't notice it until we monitored you after we released you back to your flat."

"The experiment we are conducting is dubbed 'personality-shifter program'", the voice started the explanation, so I listened. "You ever heard of multiple personality disorder?", he asked. "Yeah", I replied.

"Then maybe you've heard some stories about people with MPD, they have several personalities inside of their bodies. And the additional personalities possess a different name, gender, age, taste, character, and even skills? The additional personality might possess skills and knowledge that the original personality didn't possess. As if there were actually a few people living inside one body."

"Ya, I've heard", I responded.

"Then, this will be a lot easier to explain to you", the voice continued his explanation. "This experiment was done by 'injecting' an additional personality to an existing body. The aim of the experiment is to have soldiers and secret agents with different skills inside one body. And the government can have it instantly. No need for training. Not to mention that the soldiers must also have some skills that they would never mastered on, no matter how hard they trained."

"More efficiency in the battlefield, and of course, less budget", the voice added.

"So there you are. A former navy intelligent analyst, who have strong analytical skills, yet weaker fighting skill, injected with Billy Drake. A former army soldier who most notable for his excellent fighting skills and being fierce in the battlefield."

"We have moved Billy's consciousness, which includes his personality and skills, to your body. But, sadly...", the voice started explaining the troubleshooting part. "A small troubleshoot happened."

"Both of you should be aware of each other. Able to shift personality in conscious, and also, of course, talk to each other. When the other personality talked, it's as if there was a voice talking in one's head. The problem is, you're not. Your personality shift during sleep time. When one personality sleeps, the other awake"

Suddenly I felt enlightened. That explained what happened back in the flat for the past few days. When I was asleep, Billy awoke. And since he also owned the flat and lived in it, so he also used some stuff there, and moved some furniture he found unfit to his taste.

"Now, the preparation to reboot is done. Please lay back and relax. It will be done before you know it", the voice told me again. "Everything will be back to it was before, except now you both will be aware of each other's existence".

In less than a minute, a bright light appeared. Blinded me.

When I opened my eyes again, I was back on my bed, in my flat. I remembered clearly what happened in the room. Also the whole explanation from the voice.

A week had passed after that, and nothing strange had happened. No contact from the so called military scientist. No sleepwalking. No message on the bathroom's mirror. No personality shifting. No voices talking in my head.

Until that Sunday morning.

It was raining that day, and I was on my way home from grocery store. I turned to an alley nearby as a shortcut to my flat. A man stopped me midway and he was trying to rob me. I'm a former soldier turned analyst. I wasn't excellent at a fight, but I don't give up just like that. So I fight back.

It was a fair fight at first, but then I realized that the man who tried to rob me was stronger than me. He was also a martial art practitioner. He eventually cornered me in the alley, and pull out his knife. He clearly planned to finish me.

Then, for the first time in my life, I heard that voice talking in my head. The voice whom I believed was of Billy Drake.

"Hey, buddy. Remember the explanation when you're in the white room? The part where the voice told you that I have an excellent fighting skill and I fierce in a battle?", said the voice in my head.

"Yeah", I replied. It might look like I was talking to myself from the point of view of the man who tried to rob and kill me.

Then I heard Billy asked me again from inside my head, "wanna switch?"

I smirked.