Subaru Natsuki was a complete shut-in who unknowingly was being protected. Subaru was the wielder of one of the thirteen Longinus and the newest host for Ddraig, making him the current Red Dragon Emperor. However, his father, the grandson of Leviathan, was one of the four original Satans who died during the great war. His father wanted to protect him from the supernatural world but was unsure how.

"Give us all you got," the leader of the three thugs snarled menacingly.

With a resigned sigh, Subaru activated his boosted gear for the first time, ready to engage in combat. He glanced at the red gauntlet that now adorned his arm and wondered, "Is this my overpowered ability?"

The thugs stared at the gauntlet with bewilderment, unable to comprehend what they had witnessed. One stammered, "That's a spirit art he's using, I think? Let's get out of here!"

As the trio fled in fear, a melodic voice called, "Return what you've stolen."

Subaru turned to face the source of the voice, a breathtakingly beautiful girl with silver hair and enchanting amethyst eyes. He raised his hands defensively and replied, "I didn't steal anything." The confusion in his eyes was evident, as he genuinely had no idea what she was referring to.

Puck said, "I don't sense any malice from him, Lia."

A flying fucking cat? Subaru thought as he wondered what his overpowered ability was.

Subaru flashed a grin and struck a dramatic pose, announcing, "I, Subaru Natsuki, would be more than happy to help you find your stolen item."

"But why?" Emilia asked, pointing to herself with a puzzled expression.

Subaru took this as an opportunity to compliment her, "Well, I'm completely broke, have no idea where I am, and also, you're beautiful—" He paused, noticing the perplexed look that remained on her face, "but that's not the only reason. I genuinely want to help."

As if on cue, Puck, Emilia's spirit companion, floated towards Subaru and playfully tapped him with his paw, "Sorry, just couldn't help myself." The small, mischievous creature seemed to be teasing and testing Subaru, trying to gauge his true intentions.

What is going on? Why does she still look weirded out? Did I do something?

Emilia hesitated before remembering, "Well, I— have to go find my insignia. Thank you?"

"Can I help? What's your name?" Subaru asked, now feeling a tinge of rejection.

Emilia stuttered, "Why— are you so nice? My name is— Satella."

Puck glanced confusedly at Emilia while Subaru simply smiled, "It's nice to meet you, Satella. How about we go look for your stolen item?"

Feeling a sense of guilt, Puck chimed in, "Lia, he's really trying to help."

"I'm sorry. My name is Emilia, just Emilia. But why do you want to help me?" Emilia asked again, still puzzled as to why the raven-haired boy didn't harbor any resentment toward her.

Subaru pondered momentarily before giving the most straightforward answer, "Well, I want to. If your item got stolen, how about we look to find it?"

Emilia blinked, "Right! I can't have my insignia get stolen…."

The two began walking, with Subaru following Emilia's lead. "So, do you know where we're going?"

"Yes, well, I was trailing her before, so I should be able to find it," she replied somberly as they strolled through the Capital, hopeful they could recover her stolen insignia together.

Unknowing to Subaru, a certain red-haired knight who saw him deal with the three thugs.

As he silently continued, Subaru felt even more rejected, like his presence was a nuisance.

A few moments later.

Upon reaching the loot house, Emilia wasted no time knocking on the door.

"Password?" a gruff voice demanded from within.

Undeterred, Emilia pushed the door open and was greeted by the sight of an old man and the girl who had stolen her insignia. "Return what you have stolen from me," she demanded firmly.

Subaru, sensing danger, glanced behind him and activated his boosted gear just in time to block a dagger aimed at Emilia's neck.

"Good save," Puck complimented as Felt and Rom retreated to the corner of the loot house, visibly shaken by the thwarted attack.

"Ara ara, this may be interesting," Elsa taunted, a wicked grin spreading across her face as she dashed towards Emilia. Puck acted swiftly, conjuring an ice shield to block her advance.

Subaru examined his power, unsure of how exactly to utilize it. He was determined to help Emilia and the others, but his inexperience left him hesitant. As he watched Emilia becoming increasingly overwhelmed, his desire to assist her intensified. At that crucial moment, he heard a voice in his head, guiding him on how to harness his newfound abilities.

BOOST, BOOST, BOOST

TRANSFER

Emilia suddenly felt her power surge to three times its normal strength as a red aura enveloped her. With newfound determination, she launched a relentless barrage of attacks on Elsa. Despite dying multiple times and suffering fatal injuries, Elsa kept returning, her speed matching Emilia's boosted capabilities. The intense battle reached a stalemate as Subaru decided to boost his gear once more.

"I don't know how this will work," Subaru admitted, his uncertainty evident as he aimed his boosted gear at Elsa. He unleashed a massive torrent of energy in her direction, obliterating a portion of the loot house in a spectacular display of power.

Emilia turned to Subaru, her eyes wide with amazement, "Thank you. I don't know how I'll ever repay you for this."

Feigning nonchalance, Subaru responded with a playful grin, "That was nothing. I could've handled ten times that, don't worry." He reveled in thinking of his newfound overpowered ability and the heroine he had just protected.

However, the strain of using the boosted gear so intensely took its toll on Subaru. Feeling lightheaded and weak, he could barely stay on his feet. Eventually, he succumbed to exhaustion and collapsed onto the ground, unconscious.

Puck returned to his crystal form, remarking with amusement, "That was ironic."

"Puck, your such a dunderhead. He was nice to me," Emilia defended the fallen Subaru, her eyes filled with concern. "I don't even know how I'll repay him."

As Felt returned the insignia to Emilia, a familiar voice echoed through the room, "It seems it was fate for me to follow him."

"Reinhard?" Emilia asked, her confusion palpable.

Reinhard smiled as he approached Felt, ensuring she held the insignia again, causing it to glow. "I'm sorry, Emilia-sama, but I've been following the raven-haired boy ever since I found three thugs running in the alleyways of the Capital."

"Get your hands off me!" Felt yelled indignantly.

Reinhard touched her forehead and drained her mana, leaving her unconscious. "I'm sorry."

"Not very knightly," Emilia commented dryly.

Reinhard gazed at the moon and said, "That boy defeated Elsa Granhiert, one of the most notorious assassins known to the Imperial knights. Should I take him with me and allow him to receive his reward?"

Emilia hesitated, remembering Subaru's earlier admission. "Wait— he said he didn't have a place to stay." She determinedly glanced at the unconscious boy, "I can take care of him. I'm sure Lord Roswaal would also reward him for what he did."

While in the unconscious state, Subaru saw a fiery dragon as he stared in confusion and excitement, "So, like, are you my power?"

The voice that commanded authority echoed the landscape, "I am not your power. You are the host of the boosted gear and the Red Dragon Emperor. It seems we got sent to some other reality."

Subaru second-checked what he heard, "What? Wait, you were with me when I was in Japan?"

"Unfortunately, yes. But you have awakened the boosted gear, and we are both stuck in another world. You did have this power in Japan but never had a reason nor desire that was enough to awaken it."

The landscape of his dreams shattered as Subaru's eyes slowly opened. He looked around, realizing he was lying under a blanket and feeling the bumps and swaying movement beneath him. Subaru tried to make sense of what he had just been told, finding it difficult to believe and almost wishing it were false. Why was he such a failure in the real world if he possessed this incredible power? The thought weighed on his mind, filling him with a mix of excitement and regret for his life in Japan.

"Are you alright?" a soft voice asked.

Turning to his left, he saw Emilia sitting next to him under the blanket, her violet eyes filled with concern. "Wait, what? How'd we get here?"

"I– Reinhard came and took Felt away, offering to take you in since you defeated an assassin and would get a reward," Emilia explained, her gaze lowered. "But I said you could come with me. If you don't want to, then Lord Roswaal could probably-"

Subaru cut her off, "No, that's fine. I'd much rather go with you than some knight anyway."

Emilia's expression remained troubled, lost in thought. She couldn't understand why Subaru was being so kind to her. Even when given the option to receive an award from the Capital, he'd rather go with her. Noticing her confusion, Subaru addressed it directly, his curiosity piqued.

"Emilia, is there something I'm missing? Honestly, I don't really get why you seem so conflicted," he asked with genuine concern.

"I— don't you know? Look at me," she said, pointing to her face again.

Subaru stared at her with a slight blush, "You're so confusing. Let me say what I said: you're beautiful and gorgeous, and your name compliments your cute face."

Taken aback by his words, Emilia didn't quite know how to respond, "Thank you."

Subaru yawned, "I'm going back to sleep."

RBD is not in this fic.

Also, the short chapter is just a test run to see how this concept works.

Also, changing Subaru's dad to be the grandfather of one of the four original Satans to help justify his power with the boosted gear. (For DxD people, so it makes sense)

Subaru will most likely use his power to boost others throughout this fic, similar to how he used RBD to help.

Also, throwing in that his life in Japan was a lie is going to be my main internal conflict rather than the canon one. Since Subaru is much stronger then in canon, the events that happen will be scaled up to support it.