Where else do you store all the energy necessary for a 4-day uninterrupted breeding session?
And we can see that below all that energy storage, there is the muscular frame to support his agility.
Why does Harold play along with Justus BS?
His current plan seems to be carefully arrange for everything to happen like it does in the game. Which is a tough ask with a high chance of Harold being implicated as an accomplice of Justus, which would probably get him executed in the end. He did...
My very interpretative take on everything so far. Speculations are in italics:
Darius became the Giant and basically won
Illya survived the end of the world and is saved by Tanaka and Gil (possibly also due to Kuro as hinted to in ch 61, Kuro does after all have some limited wish granting...
In this chapter we have discount Gaare meet the honeyed-up version of the Chimera Ant Queen. We already know that any fruit born from a union with the later will end in legally-not-nuclear fire.
That image isn't mocking BL or anything, it's the socialist fraternal kiss of Brezhnev and Honecker:
https://en.wikipedia.org/wiki/Socialist_fraternal_kiss