This is an English translation of the original Japanese novel, processed through a translation tool.
There may be some inaccuracies.

Link to part 2
https://privatter.me/page/67d4f765cfec5

Sometimes they got along, but otherwise, they fundamentally found each other insufferable—repulsive, even.
That was the mutual understanding between Alastor and Lucifer.

“Alastor! So this is where you’ve been. I’ve been looking for you, you know? How about keeping me company for a little distraction? I won’t take no for an answer! Hahaha!”
“…Greetings, Your Majesty…”
It was late at night, and Alastor was on his way back to his room at the hotel when Lucifer came bounding over, visibly in high spirits.
This is going to be a hassle. Alastor had planned to rest quietly in his room tonight, but thanks to Lucifer, those plans were likely about to go up in smoke. He let out a sigh.

Perhaps it had been a day when Lucifer had managed, by some fluke, to bond well with his daughter.
Alastor had intended to brush him off lightly, nodding along with a half-hearted “yes, yes” to whatever Lucifer was babbling about. But ever since then, Lucifer seemed to have pegged him as “someone who’d listen to him until the end,” and now, whenever Lucifer was in a good mood, he’d seek Alastor out like this, gleefully unloading his trivial stories.

Alastor found all of this incredibly irritating, but he also considered that there might be some hint in Lucifer’s chatter that he could use to get the upper hand. This calculated reasoning kept him from outright dismissing Lucifer.

Normally, they’d trade barbed remarks and bicker every time their eyes met. But for Lucifer—who couldn’t control his emotions and seemed to suffer from melancholy—this must have been quite a burden.
Alastor didn’t exactly dislike watching Lucifer’s comical, rollercoaster-like shifts in expression play out before him.
In fact, he rather enjoyed it. It felt like this foolish man was exposing his vulnerabilities whenever they spoke.

“So? What’s this supposed distraction worth wasting my precious time on?”
“Oh, right—I got so caught up in stopping you that I forgot. Alastor, take a look at this.”
“…? Isn’t that just a video player?”
“Hey, hey, impatient as ever, huh? I haven’t even explained anything yet. Look here—here.”

Alastor followed the direction of Lucifer’s small hand.
On the surface of the DVD in Lucifer’s grasp were signatures—both Alastor’s and Lucifer’s.
After tracing the handwriting with a scrutinizing gaze, the two locked eyes.
Lucifer was the first to speak, asking, “Do you recognize these signatures?”
Alastor shook his head solemnly. Lucifer nodded in response, saying, “I see. You too, huh?”

The signatures themselves could easily be forged by a third party if someone tried hard enough, but neither of them could confidently declare, upon seeing them, “This isn’t mine—it’s a complete fake.”

“Here’s the thing: when I woke up this morning, this was sitting next to my bed. You get that only a high-ranking demon could’ve sent this through some special means, right? As for what’s on it… there was a note saying it’s from us in the future.”
“…Hm? Did you just say us in the future?”
“Seeing is believing, isn’t it? Here.”

Lucifer carelessly handed over a handwritten note that had presumably been tucked inside the DVD case.
…Familiar handwriting. Just like the signatures on the DVD, it bore an uncanny resemblance to Alastor’s own penmanship.

With a heavy dose of sarcasm, Alastor read the note aloud to Lucifer:

“‘To Alastor and Lucifer… From the two of us in the not-too-distant future, we’ve sent you a message in the form of this video. When watching it, ensure it’s just the two of you—Alastor and Lucifer—alone. Never speak of its contents to anyone else. If you can honor that, we promise it’ll be the most thrilling entertainment imaginable…’”
“…See? Sounds intriguing, doesn’t it?”

“…Oh, I get it. That’s why you thought to drag me into this? Still, you’ve got some nerve suggesting we watch something this shady together. Even if you’re fine with it, Your Majesty, are you going to take responsibility if something happens to me?”

“Hey, come on, don’t be so fragile. It’s just a video.”
“I happen to despise televisions and things of that sort.”

Lucifer shrugged at Alastor’s reluctant reply.

“Well, I don’t exactly watch TV myself either—drives me up the wall. But… I’m bored out of my mind right now. If watching this is what it takes to kill time, and it comes with conditions to make it fun, what choice do I have? If it turns out to be utter garbage, we can just drink it off and forget about it.”

“…Will you be treating me to that drink afterward?”
“Yeesh. You’re already assuming it’s trash before we’ve even seen it? Fair enough—I’m dragging you into this. Fine… I’ll treat you to one drink.”

“My precious time is worth a single drink? I’m insulted at how cheaply you’re valuing it, but… fine. It might be amusing to see if the future you has done something utterly outrageous.”

“Hahaha! Too much entertainment, huh? No, wait—too much talking about entertainment, Radio Demon? It’s probably just some anonymous prank, but even if it is from the future, there’s no need to freak out. Let’s watch it casually.”
“…You’re awfully quick to dismiss it as no big deal before we’ve even seen it, aren’t you?”

“It’s simple. The past can’t be changed. No matter what happens, that’s an immutable rule.”