They don't really have a choice, now do they?

If they fail they not only end Souji's life but their own as well. While he might be willing to accept that if he were alone, he can't have that happen with Chizuru.

Hijikata... they'd sacrifice him, too.

Saitou has turned to look as well and his eyes narrow defensively, but he resists making any reactive move and instead tries to focus on the only thing that may work.

I'll make an offering to you.