They were once kids who were jit with trauma, when yu is with mika and when mika is with yu, they are like children because they were forced to grow up early and fight in the bloodshed. It emphasizes that together is when they make eachother complete, safe and can be themselves to rely on eachother instead of shouldering all responsibilities. The plot is also not repeating itself, the groundwork is being set right now for the arc and there were a few subtle reminders and hints for the future as a reader who read this for the 2nd time and watched the anime for the 3rd time, I really recommend if you read the whole thing again for the easter eggs because the amount of easter eggs in this chapter is giving my heart pain with reminder of the cycle continue (e.g guren, shinya and the first, angel mika)
How could they seem so out of character? lol.
Yu did not promise shit. We already know where this is going.
Why do they keep repeating themselves? It's like they know we don't understand the plot anymore, but instead of explaining, they're just rearranging the same sentences.