When last we saw Hakuno and Saber, he had just saved Rin and Rani from an eternal stalemate (though only Rin survived); we now rejoin them as they ascent to the seventh and highest floor, where master Leonardo Bistario Harwey dwells. Even though Rin and the female Hakuno managed to defeat Leo and his servant a thousand years ago, it was only because Leo “gave up the win” of his own volition.
They arrive at a painfully gorgeous yet empty place, and are met by the Saber-class servant Gawain, who has neither the will or reason to raise his sword against them. Turns out Leo was saved by Twice Pieceman (the one who holds the grail and from which whom no servant has ever taken it) and subscribed to the ideology of Twice, maintaining the status quo on the floor.
Since humans can only survive through change, he became humanity’s enemy. After about a century, he determined no challengers would come forth, and settled into a slumber, where he remains…until now. Gawain leads the new challengers to the place where Leo sleeps—though not before Saber pays respects to her former master, whose tomb is situated on a picturesque cliff overlooking a waterfall.
As much as Saber liked that Hakuno, Rin opines that perhaps if Leo and not Hakuno had won and made it past the Seventh Floor, perhaps SE.RA.PH and humanity might not be in such a bind, because Leo wouldn’t have lost to Twice as Hakuno did. Even so, it’s likely civilization would have still fallen for other reasons related to the kind of person Leo is.
Regardless, the present Hakuno must do what neither Leo (devoted to preserving the present) nor Twice (obsessed with the past) ever could: look to the future; the only way forward for mankind. To do so, he must do what his predecessor did and win against Leo…only this time when he awakens, Leo is prepared to fight back rather than conveniently resign.
As soon as he’s up and about, Leo sics Gawain on Saber and starts attacking Hakuno, who can barely deflect his attacks with Dead Face. Saber is similarly overwhelmed by Gawain’s power, and notably neither are able to properly support one another or compensate for their shortcomings. It’s a relatively quick but still extremely epic and badass battle.
Leo orders a coup-de-grace in the form of Excalibur Galatine, Gawain’s Noble Phantasm that basically creates a facsimile of the sun itself to incinerate his opponent. While Saber and Hakuno survive the onslaught, the ground beneath them does not, and they fall, perhaps all the way back to the lowest level. Speaking of levels, it’s as if they approached a boss in an RPG without sufficiently leveling up, and simply got schooled.
Unfortunately, there’s no time to gather more power; nor is there time to ascend all the way back to the Seventh Floor: Chakravartin will be complete in a matter of hours. Just when Hakuno was his most resolved, he’s swatted down…and even if he manages to reset Moon Cell, it will most likely mean deleting the last thousand years of history.
Since that history contains the defeats and amassed negativity that led to his creation, restoring Moon Cell will presumably claim Hakuno as well, meaning history could easily repeat itself with no more hero to correct it again. Still, I’m sure he, Saber, and Rin can figure something out.