Ultimate Highschool DxD

After waking up in the morning, Issei had breakfast with everyone. Everyone seems to be really excited regarding their training session. After finishing breakfast, all of them gathered in the Gremory palace's courtyard. Ravel went with her peerage to the Pheonex territory to meet her family.

"Everyone, are you all ready?"

""Yes, Ise!""

"Don't expect the training to be easy. It might even be fatal. So, I want to ask you something. What do you want to take part in this training?"

""We want to become stronger.""

"If it's just about becoming stronger, I can use my magic to enhance all of your powers."

""No, we want to become stronger by our own hard work."

"Alright then. We won't do our training here. I talked to Zeoticus and he allowed me to train all of you at an isolated mountain within the Gremory territory."

Saying so, Issei summoned a big teleportation circle. All of them stepped inside it and we're teleported in a remote mountain of the Gremory territory. A mansion has already been built there by Zeoticus and arrangements have been met to meet all basic needs like food and clothes. After teleporting there, everyone was assigned a room each.

"Since this place is isolated, you all can train here with no restrictions whatsoever. The mansion has an impenetrable barrier, so you don't need to worry about it. Now let's begin!"

Issei gave each of them different training methods. They still had two more weeks before the youth gathering. He first decided to train Kiba and Xenovia.

"Xenovia I want you to swing Durandal a hundred times every two minutes. And also swing it with all your strength."

"That's going to be a bit hard. Durandal is very heavy and I might lose balance while swinging it continuously. But I'll do it."

"Don't be hasty, there's catch. There shouldn't be even be a single vibration in the surroundings while you swing Durandal."

"What?!! That's impossible!! If I apply all my strength and swing it only once it can create a huge crater. And you are telling me that there shouldn't even be a single vibration?!!"

"It's not impossible. Let me show you."

Issei took Durandal and swung it with all his strength. But he sing it a hundred times within just five seconds and there wasn't even a flow of wind. It felt as if nothing ever happened.

"See and that was not even my full speed. I did that in only five seconds and I'm asking you to do it within two minutes. And until you can't do even one strike without causing any damage, you're not allowed to stop. Get started. Now!"

Xenovia began swinging the sword. She began as quickly as possible so that she can at least a single strike right. Issei gave that regiment to Xenovia, considering the fact that she focuses more on power rather than techniques. As a result, her biggest weakness is her speed and lack of control over we power. That's why, Issei told her to do it a hundred times every two minutes without causing a single vibration. Issei told her to do it without causing any vibration, because Xenovia can't control Durandal's power. So, this is necessary for her.

He then uses his magic to create a clone of Kiba. With the exact same power, speed and way of thinking and fighting. He tells Kiba to defeat is own clone.

"Defeat your clone Kiba. This clone has the same power, speed and sacred heart ad balance breaker as you. He uses the same techniques and he has he exact same mindset as you. But remember that you are the original while this is only a clone. Try to find a loophole and utilize it. Kiba if you want to surpass your current limitations, then you need to defeat yourself."

Then Kiba began fighting with his clone. Issei went to Raynare, Kalawarner and Mittlet. He told the three of them to battle against each other with full strength. He then went to Asia and told her to concentrate on her 'Twilight Healing' and try to comprehend it's power. He then went to Gasper and told him to try and engulf his entire body in shadows and try to control them

He then went to Koneko. He wanted to train her sage powers. So e decided to tell her the truth about her past.

"Hey Koneko, I need to say something important to you."

"What's it, Ise?"

"Shirone...." Immediately Koneko's lips turned into a frown. She didn't want to hear that name.

"Where did you hear that name?"

"I know your past, about you and Kuroka. But you misunderstand."

"What do you mean?"

"You and Kuroka were once the daughter of a Nekoshou named Fujimai and a human. Both of you were orphans. Then the House of Naberius took Kuroka in. They did several harsh and cruel experiments on Kuroka. They wanted to do the same to you. So, to save you Kuroka killed her master and ended up becoming a criminal. But she didn't mind it one bit. Later when you were taken in by Sirzechs, she was relieved because the Gremorys are known for treating their servants like families. She has been running around since then to save herself. She was never drunk on power. She did all that to save her sister whom she loved the most. So, please don't hate her for what she never did and accept your heritage."

After hearing Issei's words, Koneko couldn't control her tears. Years overflowed from her eyes. She never gave a Hought that her sister might not be a bad person. She felt sad that her sister. But she never once tried o understand her sister. Issei hugged her tightly to comfort her. After she calmed down a bit. Issei still kept her in his arms and said:

"Shirone, don't cry. I promise I'll reunite you with Kuroka. I swear I'll make you both happy. I'll never let you feel so sad ever again."

Shirone calmed down completely. She was happy that Issei cared so much. Her love for him became even deeper.

"From now on you are Shirone Toujou. I swear that I'll make your sister Kuroka Toujou. Now let's begin our training."

Issei told Shirone to transform into her Nekomata form. He took her inside his pocket dimension and entrusted her to Magari to train Shirone from scratch. He decided to train Rias and Akeno personally.

"Rias and Akeno, I'll train both of you personally. Akeno I want your fallen angel power. There is no point in denying who you're, if Shirone can do it then you can too. Try to use holy lightning. Rias I want you to activate your Power of Destruction."

After both of them did what Issei asked, Issei trained them. He taught Rias on how to control her Power of Destruction. To transform it into several shapes and sizes and to control it's mass and density. He taught Akeno how to summon Holy Lightning properly. He told her to concentrate better and increase the input of demonic power(devils use demonic power as power source for their magic, instead of mana). Then he started meditation to control his powers. He still isn't strong enough to take down Trihexa. Trihexa can't be taken lightly. Even all the Gods and super devils and the two heavenly dragons, even if all of them work together they can't defeat Trihexa. In his weakest state, he is still ten times stronger than Ddaig and Albion together in their prime. So, in his strongest he is literally unbeatable. Issei can't defeat him with all eighteen longinses and his demonic power of extinction. He needs to unlock the other eighty-three demonic powers that flow within his blood. He needs to unlock them.