Rebirth of a Fusion

Awoken

Izuku shot right up in his bed as he looked out his dorm room window and muttered, "Same damn dream again. Why am I having visions of fighters that have weird Quirks? On top of that, I still haven't unlocked One for All yet. What is taking my predecessors so damn long?"

He then stopped short and said, "Since when do I swear?"

He shook his head and he heard a voice, "Hello Izuku Midoriya."

"Who are you?" he asked looking around. "Where are you?"

"I'm right here Izuku," the voice said once more with a bit of amusement in it's tone. "I've always been with you. Since the very day you were born."

"Who are you?" Izuku asked again.

"I am Gogeta," the voice replied. "We are one and the same Izuku. I know all about you. Your fears, your hopes, your dreams, your love for Uraraka, One for All, and everything else. Now then, allow me to tell you a story. A story of the greatest fighters in multiple worlds."

Time skip

Izuku and his class were now eating lunch and Ochaco asked, "Something wrong Izuku?"

Izuku, who has been thinking of what Gogeta had told him earlier that morning, just said, "Uh? Oh yeah, everything's fine."

"No everything's not fine," Ochaco said looking down at her oldest friend. "You've been down ever since this morning. What's going on?"

"Nothing," Izuku replied as he finished eating and got up. "I'll be in the training room if anyone needs me. Which isn't likely."

As he walked away, Ochaco said, "Do you know what's going on with him?"

When they shook their heads, Ochaco sighed and said, "He won't tell me what's wrong. I just want to help him."

Time skip to USJ

I believe that it's time to become one, Izuku, Gogeta told him. I have a feeling that you'll need my power here. Do you want to begin the process?

How long will it take?

Only a few minutes, but you'll need a powerful emotion to force it out and then you can do incredible things.

...Do it.

At that moment, a black misty portal appeared below them and Aizawa said, "Stay back! Those are villains!"

It is done, Gogeta said. All that's left is an emotional up... heav...al. I have an idea.

Izuku, realizing the idea, replied with No way will I be unleashing all of my pent up rage just so I can use your power.

You must! Gogeta barked at him. It is the only way you can unlock my power! These villains won't show any mercy to you or your classmates. They will aim to kill and the only way to beat them is to use my power and make it your own and the only way to do that is through an emotional upheaval! Listen, I know that you don't want to take a life, trust me, I had a son who knew what that's like, but that's the only way to defeat your opponents at times. My son had to learn that the hard way. At least don't do this for me or for yourself, do it for the people you love. For Ochaco, for your mother, for your friends. It's the only way you can survive... Are you ready?

Izuku took a deep breath, closed his eyes and said, Lets do this.

It'll take a bit, Gogeta replied. Be patient, I'll tell you when it's time.

Time skip to Nomu attack

"Aizawa-sensei!" Izuku shouted as Nomu threw Aizawa into a wall and dashed towards the teacher before punching him in the face over and over.

"HAHAHAHAHA!" Shigaraki laughed out. "Good Nomu! Now finish him!"

It's time! Gogeta shouted as Izuku's eyes widened in rage, before narrowing as he screamed and a column of pure energy spiraled up into the air.

Everyone looked on as Izuku continued to scream as the white aura turned a dark red, before turning gold, then gold with sparks, then gold with larger sparks, then an orange-red and lastly turned to blue. Everyone's eyes widened in shock, awe, and a bit of fear as they all went down to one knee because of the pressure of the power he was exhibiting. 

"You two," Izuku said pointing at Nomu and Shigaraki. "Will die!"

Izuku then shot forwards as his blue aura grew bigger and his fist collided with the monster before he kicked it and leapt backwards and holding his hand up in the air and a sphere of rainbow energy formed.

"Your own bad energy will be your undoing!" Izuku shouted before throwing it at the Nomu who then punched his forehead, before wailing in pain and exploding with positive energy as a male with brown hair and black eyes dropped to the ground unconscious. "Now then Shigaraki, where were we?"

"Who are you?!" the handy villain shouted out in anger. "No one can do what you just did!"

"I am Gogeta!" Izuku shouted right back his blue eyes shining with power as he raised his power level to even greater heights. "I swear to put an end to all evil in the universe! To bring peace and hope to the hopeless! To put fear into the hearts of all evil men and women out there! To bring an end to villainy! I am... Gogeta! The Godly Hero of Hope!"

"We must leave Shigaraki," Kurogiri said to the ringleader. "We can't win this battle."

"Very well," Shigaraki snarled. "Listen well Gogeta! I will be back and when I return, I will kill you and all you love! That's a promise!"

"I look forward to out next battle, Shigaraki," Izuku replied as he flared his energy. "And next we meet, I won't allow you to live."

The two villains then left and the heroes busted through the entrance and All Might exclaimed, "We are here!"

Izuku then went back to base form and dropped into unconsciousness and the last thing he saw was Ochaco rushing to his side.