I wouldn't be so hard on Ikta. While he knew they exist theoretically, they had never been used in any war before. It's like the terrorists automatically thinking the USA brought a railgun or laser cannons to the field when they spied some big machine in the distance. Furthermore, apparently the theocracy hates all technological advances (or maybe everything powered by the spirits), so despite seeing the blimp earlier, his instincts still worked against him.

It proves nothing you, and I, immediately realised they must be cannons.

And I wasn't thinking about simply sex, rather a marriage and a family. However, the fact Yatori thinks nothing of Ikta's numerous dalliances certainly speaks against it. But why would Ikta then promise to stay with Yatori? That makes no sense. When a man or woman marries someone, they primarely will stay with that person and the forthcoming children. Is Ikta basically saying that neither of them will ever get married and instead they will just hang around as buddies for no particular reason for all eternity? I'd imagine the Igsem family would want heirs from Yatori. It's a centuries old noble family or something. They wouldn't want it to end. Is Yatori going to tell her future husband that by marrying her, he will also marry this lazy dude Ikta?