Author's note: Minor changes, I'll be changing to the Master of Durability to Mastery of Endurance, they are the same thing but Endurance sounds better to be honest.
Author's note 2: I'll clarify something here, Mc has the knowledge of his past life, and the knowledge of the original Jinrang, but he doesn't know DxD all too well, he knew how the plot started, and knew about Sirzechs Lucifer's power and capabilities, (I decided this way because I'm too lazy to write the whole finding out about supernatural shit, but it looks like I'll have to make some changes.) this is because when I started making this fanfic Jinrang's backstory wasn't revealed, I'll somehow squeeze the backstory of the MC in this later.
After the meeting went down, Rias decided on doing something like a training arc, Jinrang offered to train Koneko, Kiba and Issei and they happily accepted his offer.
Plus, Jinrang needed to do training of his own, he wanted to re-create techniques of his fellow kings, specifically the Iron fortress, and the ultimate fist.
From his memories, Jinrang had experience fighting the creators of these techniques, so he could definitely try to replicate them, neither of them required special talent or anything of the sort, so he wanted to give it a shot.
The Iron fortress was a technique of Gongseob Ji, it was the best defensive, or the best technique to maximize the body's hardness to endure as many attacks as possible.
The Ultimate fist, was a punching technique of, Taesoo Ma, it was probably the strongest striking technique Jinrang has ever experienced, it combined Taesoo's Mastery of Speed and Strength, to create a one hit one kill punch.
(These techniques are from OG Jinrang's memory, so he decided to take it. No, Jinrang won't be learning Iron boxing because that's hella difficult, Iron fortress is basically having a rock hard body which is much simpler to do. As for Ultimate fist, well that's one single devastating strike, not a completely different fighting style like Iron boxing, plus Iron boxing wouldn't really fight Jinrang either way, and also because I'm already having difficulty on writing fight scenes as you may have noticed, so I really don't wanna make it worse than it already is.)
However, this technique was relatively new, so Taesoo wasn't able to use it properly more than once per day, and Jinrang was hoping to fix this with the mastery of endurance.
The Devils and Jinrang were making their way up in the mountains, the close-combat fighters had very heavy backpacks on their backs for training purposes.
Issei had the smallest one, Koneko the largest and Kiba was in the middle.
Issei was panting and looked like he was dying, but he didn't complain he knew exactly what would happen to Rias, and he wasn't gonna let that slide.
Issei Hyoddou, was slowly maturing into a devil worthy of the boosted gear. Jinrang played a big part in this, Issei had someone he could respect, and he wanted to be just like him.
Issei practically saw Jinrang as an older brother, someone that represented strength and dependability.
The group finally made their way up the mountain and got themselves all settled in.
Now, it was training time.
Jinrang had a training session with Issei first, the two went down to the basement, there was a rather large gym the estate was equipped with.
The gym equipment was nothing to scoff at either it had everything you'd need, plenty of weights too.
"Issei, I'll set a goal for you before we start this training arc of yours." Jinrang said to Issei.
'Training arc?' Issei raised an eyebrow at that.
"I'm listening." Issei said focusing his full attention on Jinrang.
"In 13 days I'm gonna prepare your body, as of now you do not met the conditions to achieve mastery, your goal is to make your body as strong as possible, and learn how to fight properly."
"A-Alright, where do I start?" He smiled.
"We're gonna be fighting a whole lot, me and you. Oh, you're forbidden to use Boosted Gear for now."
Issei's smile disappeared immediately. "Will I be alive after 13 days?" He muttered to himself.
"Don't be so dramatic, let's start."
Issei went into a fighting stance, and rushed towards Jinrang, throwing a lackluster punch which Jinrang didn't even bother to block.
Issei's eyes widened a bit, before he struck his stomach again, Jinrang didn't block it this time either.
'No way.' Issei thought to himself, 'Am I really this weak?!'
The smaller boy continued attacking, a kick here, a punch there but nothing seemed to be working.
"I see, I've quite a lot of work to do." Jinrang said to himself.
"…Sorry." Issei apologized while looking down.
"Don't be, you've got nothing to be sorry for." Jinrang said while putting a hand on Issei's shoulder.
The training session went by pretty well, Jinrang mostly focused on the basics, he taught Issei to use his feet when he throws a punch, and to basically load in his bodyweight behind each strike. Issei's talent in hand-to-hand combat was quite good, he absorbed things quickly and easily.
After Issei got the basics down, he sparred with Jinrang again, but the outcome wasn't much different, The bigger boy took all of his attacks without taking a step back or even flinching.
Jinrang punched Issei once, though there wasn't much strength in it, but to his surprise Issei managed to stay on his feet albeit with much difficulty, but hey it was just the first day.
After a couple more minutes of Issei using Jinrang as a punching bag, and him hitting back once or twice, Issei stopped while he panted from exhaustion.
He also had tears in his eyes, since he wasn't really used to pain all that much. Sure, his friends punched each other in the face here and then, but Jinrang's strikes were completely different.
"Haa… what are you… made out of?" Issei questioned between breaths.
Jinrang just smiled, "You'll be able to take punches like me soon enough, but before that you have to get used to two things. First, when you see an incoming punch make sure not to close your eyes, actually never ever close your eyes in a fight, it might be difficult at first but you'll get the hang of it. The second thing is pain, you'll eventually get used to the feeling of a punch landing on your body and face."
"I-I'll try." Issei croaked out, too exhausted to even talk.
"Good, let's finish it today. You did well, but tomorrow I'll also be punching you in the face."
"T-Try not to split my skull." Issei joked nervously.
"No promises."
Issei limped out of the gym and it was just Jinrang left.
'Guess it's time for my own training.' Jinrang thought to himself.
Jinrang summoned his familiar the gorilla which he named Harambe, after that he explained his ideas to it, the gorilla understood what he was asking, although it couldn't speak it understood its master's speech.
Jinrang took off his shirt and leaned against a wall, hands behind his back, and stomach completely exposed.
Harambe stood in front of Jinrang, and punched him right in the guts, Jinrang grunted but still smiled, the gorilla's strength and punching power was sufficient for his training plan.
For 20 minutes the gorilla kept on hitting and hitting him, Jinrang grit his teeth and endured the agonizing pain traveling from his stomach to his upperbody.
"Punch harder!" He ordered Harambe, who roared and punched with more accuracy, more strength and precision.
Blood dripped from the edge of Jinrang's mouth, but he didn't give in at all, he endured some, and then some more.
After 40 minutes, Jinrang was completely exhausted, he dropped down on the floor struggling to even breathe.
"G…Good, thanks Harambe." Jinrang managed to say, and Harambe nodded happy to help his master.
Harambe disappeared using a magic circle, he went back to the familiar forest to rest. He wasn't as exhausted as Jinrang, but going full strength for that long was still quite draining.
'This… is a lot harder than I thought.' He thought grunting while struggling to stand up.
Eventually he managed to stand up and put on his shirt.
He quickly his way up to the living room.
Akeno was preparing lunch in the kitchen, 'Sorry Akeno, but I'm too exhausted, I'll sneak past and lie down for a bit.' He thought to himself.
But as he was sneaking by, the floor creaked under his weight, Akeno turned quickly and saw him, frozen in place.
She smiled but it froze seeing the blood on his mouth, which he forgot to wipe.
She ran over to him "What happened? Are you okay?" She questioned worriedly, while she wiped the bloody away.
"Uhh… Endurance training." He explained shortly, while smiling nervously.
"What kind of- Oh." She quickly realized what he was talking about.
"Yeah, sorry for worrying you."
"…Be careful." She said to him while caressing his face.
"You… aren't against it?" Jinrang questioned while grabbing her hand that was on his cheek.
"I trust you know what's best for you, and you know more about this… 'Mastery' than I do." Akeno said.
Jinrang stood there for a second, he didn't think Akeno would be okay with it, after all this endurance training wasn't very… orthodox.
"You must be hungry after training, I'll go get everyone." Akeno said.
"Alright, I'm dying to taste your cooking."
Jinrang said to her with a smile.
Akeno giggled and went to gather the others.
Jinrang stood there for a second watching her move away, before he went and sat down on the couch in the living room.
'Endurance is going to take a while, I didn't realize how scary you were… Gongseob Ji.'
He touched his abdomen and hissed in pain.
'If you didn't loose your leg, I wonder how strong you would have been? You shitty monk.'
He chuckled, but the soreness stopped him right then and there.
'Okay, tomorrow I'll train my fists, Taesoo's ultimate technique is too strong to pass up. Gongseob Ji is the Greatest Defense, Taesoo Ma is the Greatest Striking Power, learning both of them will push me to a whole new level.'
'Even if it's a cheap imitation, I'll do my utmost to re-create them.'
Jinrang was so deep in thought that he didn't notice Akeno and the others who came in to the room.
"What are you thinking so hard about? About me perhaps?" Akeno joked as her face came into his view.
Jinrang's heart skipped a beat. "Sure." He said with a smile, while he pulled her head closer and kissed her cheek.
Akeno blushed but smiled happily.
Meanwhile, others watched the two with differing reactions, Koneko stared with a blank face, Kiba was happy for his two friends, Issei clicked his tongue, Rias's Eyebrow twitched ever so slightly, and Asia blushed while sneaking glances at Issei.
"Enough flirting you two, let's sit down and eat first." Rias interrupted their moment.
"Aww, we were just getting to the good part." Akeno whined.
"Get to it in private." Koneko said.
"Yeah, what she said." Issei added, taking her side.
Kiba chuckled at this exchange and followed Rias to the kitchen.
Akeno and Jinrang looked at each other before laughing as well.
The group finally sat down to eat they mostly talked about their training regimes, and how to improve in certain aspects Jinrang told Kiba to try to improve his raw strength, most knights lack that.
As for Koneko, she should focus on speed for obvious reasons. Basically, Koneko should learn from Kiba, and Kiba from Koneko, that would be the best course of action.
Jinrang already has his hands full with Issei, and then his own training, plus he couldn't really teach Kiba anything he was a swordsman, Jinrang fought with his hands.
Normally, learning Hand to hand combat would be beneficial for swordsmen if they lost their weapon, however Kiba's sacred gear could summon as sword whenever he wanted it, so he didn't really need to learn hand to hand combat.
Training aside, Everyone complimented Akeno's cooking but the only compliments she wanted to hear were from Jinrang.
She was sitting next to Jinrang and kept staring as he ate, the sight brought a smile on her face.
Jinrang eventually ate everything that was left on the table, and complimented each dish. His stomach was also quite happy to receive such delicacies.
"Thank you for the meal Akeno, but I believe it's time we head to the baths." Rias announced while clapping her hands
"The baths!" Issei jumped up happily, his imagination running wild already.
'It seems there are some things that I can't change much.'
"Ah, do you want to bathe with us Issei?" Rias asked him with a smile.
Issei froze, facing such an unexpected question.
"You don't mind being with Issei right? Asia?"
"N-no…" the shy yellow-haired girl spoke meekly.
"What about you Koneko?"
"I do mind… and I'm sure Akeno does too." She spoke shattering all of Issei's dreams, while glancing at Akeno.
Akeno looked at her as well, and noticed the slight smirk on her face, while her eyes were signaling something.
Akeno understood what she was suggesting.
"You guys go in first, after you've finished me and Jinrang will go." Akeno spoke.
"I will?!" Jinrang asked while his neck snapped towards her.
Rias smirked slightly before she came close to Akeno and whispered something, Akeno blushed really hard at whatever she said.
"Let's go everyone! Hot springs await." Rias said and everyone followed her, except the two lovebirds.
'She really… is quite forward.' Jinrang thought, while rubbing his neck.
He wasn't embarrassed, but he was indeed surprised by her words.
Meanwhile.
"She's head over heels for him, that Akeno." Rias said, while sitting down in the spring.
"Yes, I didn't know Akeno had such a side to her." Koneko responded.
"I-Isn't that a good thing? T-They love each other deeply." Asia spoke softly.
"Asia, It's definitely not a bad thing, but those two haven't even known each other for a month." Koneko explained.
"R-Really?! I thought…" Asia trailed off.
"But somehow, they understand each other really well… it's like those two are made for each other." Rias said, a smile creeping up on her face.
Remembering when she teleported in their room just to see her two friends sleeping together, while smiling made her feel happy for Akeno.
But, she was also a bit envious of her, having the freedom to choose your partner wasn't available to her, but now she was given a chance and she wasn't planning on wasting this chance.
And… like her dearest friend, someone also caught her eye, a certain-browned haired boy with a red gauntlet.
Author's note: Sorry for not uploading, my irl schedule has gotten tougher and tougher, I'll try to upload at least 2-3 chapters per week, no promises though.