the last dialogue box dokja says is better translated as "see you soon, yoo joonghyuk" but "let's meet again" is what the unofficial english orv translation uses

the full conversation in the webnovel is actually
“…If I use this, you can't be resurrected."
"That's why you are going to use it. It would be difficult if I came back again as a demon king."
"…"
"What if the scenario ends up being ruined? You should stop thinking about it."
Yoo Joonghyuk glared at me without speaking.
「 Do you have an idea? 」
I just laughed at his question. Yoo Joonghyuk hesitated before eventually pulling out a sword.
The Heavenly Sword of Gathering Clouds. Ame no Murakumo no Tsurugi. It was a sword obtained from Yamata no Orochi in Peace Land.
Yoo Joonghyuk spoke in a somber voice, "I hoped the moment where I had to use this would never come."
"Me too. However, now is the time.”

and kdj's last words are
“Don't worry about it.” / “It was a really great story. Isn't that right?” / “Let's meet again, Yoo Joonghyuk.”

in case you wanted to be sad