Fantasy Assassin in a modern world

When Loki gained the ability to use inner energy, the first thing that came to his mind at that time was if it was possible to merge his mana with his inner energy. The two powers came from completely different sources and even though they had some similarities they worked differently. 

Inner energy was produced by one's body and like any body part, it could be strengthened with proper training. The stronger one's body becomes the greater the inner energy it could store. 

On the other hand, mana was the spiritual inner energy produced by the world. To strengthen one's mana supply one needs to become more attuned to it. The greater one's understanding of mana the faster one's mana supply increases. It also helps if you were at a spot that has concentrated mana. 

When the two inner energies meet one would try and suppress the other. In Loki's case, his mana was stronger than his inner energy thus making his inner energy fall behind. After a bit of practice, Loki was able to use the two different powers in tandem, and his mana no longer rejects the inner energy as strongly as before, the same can be said with his inner energy. 

Loki was unsure of what would happen if he forcefully combines the two different forms of energy. It would either destroy him or it would increase his strength greatly. There was also the possibility that nothing would happen. 

Under normal circumstances, Loki would never use something that he wasn't sure of, but the current circumstances were anything but normal. 

'Am I really going to make such a drastic bet for people I barely know?' Loki looked at the unconscious bodies of the Twin Stars and the Grandmasters, at that moment he was once again reminded of the death of his sister. 

'Damn it, even now I can barely forget that day. Even now you're making me do things the hard way.'

Loki sighed as he strengthened his resolve. Loki gathered his mana and circulated it through his entire body, once it was moving smoothly Loki released his inner energy. 

...

The young man was about to attack when he suddenly felt an intense pressure emitting from Loki. He could not understand it but warning bells were sounding in his head. The young man then noticed that Loki seemed to be sweating profusely and his body was trembling. 

'What is happening to him? It looks like he was trying to do something. Well, now that he looks so weak this could be my chance to finish him off.'

The moment the young man had that thought, Loki casually walked towards him. The young man was then surprised to see that Loki had arrived before him without making a sound. He then saw Loki casually throwing a punch at him. 

The punch was so slow that under normal circumstances the young man would've evaded the strike while yawning but for some reason when he thought of evading, Loki's fist was already inches before him. The young man could only raise his left arm to defend. 

The young man was going to counterattack after defending against Loki's strike that was his initiation but the moment the punch connected the young man was blown away. 

The young man felt his left arm throbbing and he heard the boned on his left arm slightly cracking. The young man couldn't understand what had happened, his body that was harder than steel was actually damaged to such an extent. It was not a trick or technique like before, Loki had used brute force and almost broke the young man's arm. 

The young man was still startled when he noticed that Loki was once again in front of him. He quickly evaded and then he saw the wall that was behind him crumble. The young man backed away and distanced himself from Loki. Yet Loki stuck to him like glue, the young man then saw in the corner of his eye a needle on the ground. 

The needle exploded at the young man's feet causing him to stumble. Loki took this chance to attack. the young man unconsciously raised his broken left arm, but Loki's fist bypassed his defense and hit him squarely at his chest. 

Loki had already hit the young man many times before, at that time Loki's attacks were nothing more than an annoyance, but this time the young man could hear his ribs cracking. The young man even felt his lungs getting damaged and it was getting harder to breathe. 

For the first time in his entire life, the young man was feeling something he never thought he would ever feel. The young man was feeling intense fear. As the fear was encroaching on his very soul, the young man saw that Loki was no longer moving. 

He then noticed that Loki was sweating bullets and was panting heavily. Loki was already on his knees his entire body trembling. Loki had reached his limit, whatever it was he has done to drastically increase his strength had finally taken its toll on him.

Yet despite Loki's current state, the young man did not dare approach. The young man was so frightened that he even forgot his mission and was unable to move. 

On the other hand, Loki who was barely conscious was confused as to why the young man was not finishing him off. As the two stared at each other, the young man received a message. 

"The Elite Dragon Brigade has broken through the Star of Dawn's blockade and is heading your way. ETA is ten minutes, have you completed your mission?" 

The young man finally woke up from his fear when he heard the voice of his commanding officer. Hearing his commander's voice the fear he felt had diminished a bit. 

"Negative, an unknown factor has intercepted me." 

"... Fine, retreat for now and give me a full report when you get back." 

"Roger." 

When the young man heard that he could finally retreat he could not help but sigh in relief. The young man did not even think twice as he quickly escaped the premises, he did not even dare look at Loki afraid that Loki would suddenly appear before him. 

When Loki saw the young man retreating he was confused, but at the same time relieved. If the fight continued he did not know what would've happened. He still had a few cards to play, but he was unsure if that was enough. When he was sure that the young man was gone Loki tore off the make-shift mask he was wearing and crawled closer to the unconscious Twin Stars.. Once he was near the Twin Stars he laid on the ground closing his eyes.