Truthfully, James himself feel skeptical and doubtful for Rein to rely on him killing an existence that can be called as the strongest. In fact, if he wants to say it bluntly, James wants to ask Rein whether his head has some screw loose or not.

'However, there is hope if I can use Rein's power as mine.'

Who is Rein in the first place?

He is an existence that will become the strongest existence than anybody, even the god of creation itself! Therefore, if Rein is able to transfer his power, defeating Satan (Lucifer) is not a nonsense. No, it is inevitable.

"But, what do you mean by traveling to the other world?" (James)

Instead of answering him, Rein ask him a question, " What is the current condition of my body?"

"What do you mean, it's...--- ah!!" Before ending his sentence, James notices one problem.

Rein himself already say it. He is a supreme that was able to seal Satan BUT with a huge price. Sacrificing his companion's life and most of his own power, he is far from the optimal state. Moreover, James needs to consider the cost for him able to be alive(?) and talk to him by saving his life.

In other words,

"It's not enough...." muttered by James

Bitterly smiling, Rein said "Yes, it's definitely not enough for my current power to kill that guy. Just creating this opportunity has already expended almost all of my power. If it's that easy, I wouldn't even summon you. Instead, I will kill that bastard personally with my own hands."

True, if Rein was able to restore his power, he can just come to James's world and kill Satan with his own hands. If not, why would he even save James in the first place?

".... I understand. However, could you explain to me for how I gain power by traveling to other worlds? No, before that do we even have time before Satan exterminate it all?"

"Ah, for that you don't need to worry.One of my companions has the power stop the action of Satan by freezing space and time itself. Of course, that is possible by combining with my power too."

Hearing that, James is seriously speechless, "... I know I'm not the one who's supposed to say this but, aren't the other me is too omnipotent ?"

"hahaha! well, can't blame anyone for that. if I can't even do this kind of small feat, I will never dream of defeating Satan himself." (Rein)

small feat?

controlling time and space that most Gods are unable to do is a small feat?

"pft, that's also true. ..... okay, my first question. For traveling other worlds, is it something like gaining experience or new power?"

"Hmmm...." after pondering for a while, Rein gives an unexpected and vague answer, "Maybe, but maybe not too. I'm really sorry to say this but, gaining power is not an easy thing to do, even for me. True, your adventure to other worlds is for gaining power, however, it is not definite for your travel can have powers sufficient enough to kill that bastard."

From that, James learns one thing. It means that Rein was that desperate.No, to be precise he has no more solution to defeat the 'cheaty' boss. In fact, this solution itself can be said as a gamble with very low probability to win. That show just how much cornered Rein is.

"Even so, I must do it."

Low chance to win? not definite?

So what. For James, that is something he already knows and tastes during the time he chases his own dream. On his goal, he may stumble someday, he may also give up middle way and obediently follow his father's footsteps. The future is not definite. No matter how strong you build your foundation for the future, it can crumble with just one small event. there's no such thing as smooth sailing for all of your life.

Noticing James determination, Rein is pleasantly surprised, "Looks like your mental strength is really strong. You really have a rough journey in your life."

Nodding, James answered, "Yes, I'm sure you know my life, but it was never always a happy thing. No, it was constantly bumpy and narrow. Even though I was determined to become a great writer, there was never a moment I didn't worry. Can I really succeed? isn't it better to have smooth life by submitting to my father? Those kinds of things still linger in my mind."

"Even so, you didn't want to give up on your dream right? after all, you who was constantly obedient at all time even rebel on your father in order to chase it."

with a determined voice, James answered, "Yes, that's just how precious my goal was. I know that writing is hard to live stably if your story is not interesting. Moreover, it'll not be necessarily be accepted by the reader. This situation is also the same. a thin hope to defeat Satan? meaningless journey? screw that! even if it is so, it's not a reason for me to stop! I will decide myself how do I live. Even though it can be miserable, my fate is my own to control!"

A reckless answer.

However, for Rein that is the best he hoped to hear. In this hopeless situation, being realistic and depressed is not what he wanted from him. All he wanted was one thing, which is the feeling to strive no matter how hopeless the situation is.

that is the core and identity of Supreme.

With a bright smile, Rein said, "Well said, looks like my gamble has some worth to stake on it after all."

"Yeah, I can't promise you to defeat him. But, I can assure you one thing. I WON'T and EVER give up this choice no matter how difficult it is" (James)

"..... Thank you." (Rein)

Hearing that James can't help to tease him, "Hey, what do you even need to thank me for? Say that after I kill that bastard okay buddy? "

"..haha. Ok then. I will do so." (Rein)

After a bit of laughter, James ask a question, " So, do I inherit your power now? After that should I just go to a random world?"

Shaking his head Rein answered, "No, you will inherit my power, but you can't travel to the other worlds yet. There's something you need to do."

"Which is?"

with a faint smile, Rein answered "Training. Although your mental strength is good enough, that doesn't mean you are good at fighting right? Therefore, I want you to ingrain the art of fighting and killing with your own flesh and blood to survive."

Surprisingly, James calmly respond, "Oh, sure, is it by you? do we start from here?"

With this response, Rein can only bitterly smile.For James growing up from an urban city and free from seeing war, he expected him to complain or make excuse to avoid it. However, he can only see that James is expecting it. Heck, it looks like that to him, it is a natural thing to do.

arranging his feeling, Rein answered his question, "No, I can't teach you. I'm not the optimal person for you to teach since I don't know how to. Therefore, i will call someone who can teach you. two people to be precise."

nodding his head, James said, "I understand. Then, who are going to be my teachers?"

with a small smile Rein give two names he didn't expect at all.

"Kazami Yuuji and the queen of shadows, Scathach."