Subaru laments that he could not do anything or save anyone, and has no options left. Exhausted, he suddenly takes off running at full speed as if he's made a decision... To save Emilia, Subaru approaches Crusch to negotiate the formation of an alliance. His terms are a bit difficult for Crusch to believe, but she can see that Subaru isn't lying.
In other words, the fuel needed 
to subjugate the mabeast
Kurz gesagt: Die Zerstörung eines Monsters,
das die Welt seit Langem terrorisiert, …
Ça te permettra d’éliminer le monstre
qui terrorise la population
Em outras palavras, o combustível
 necessário para derrotar o majuu