As Itsuwa searches the internet for a sexy outfit to counter Kaori’s maid assault, Knight Leader stands ready to instruct Kaori on how to act like “a proper English lady” (and presumably dress like one, neither of which appeal to her), while a chance encounter between Touma and Misaka results in the latter getting “overcharged” at the vending machine.
Touma comes home to Index with instant yakisoba, but their meager repast is interrupted by a call from Tsuchimikado, whom Touma demands to keep it short, and he does: “Get your ass to Britain.” A moment later a knockout gas grenade is thrown into the apartment, and Touma and Index pass out.
At some point between then and when we next see the pair, they were given a choice to board Tsuchimikado’s supersonic jet for travel to Britain, but Touma chose the more comfortable alternative of commercial air travel aboard “Air Bus 365” (which sounds more like a make and model of plane than a flight number).
This would be fine, with the biggest problem keeping Index fed and quiet, but due to Touma’s boundless misfortune, the airliner they happen to board has been infiltrated by anti-Britain terrorists with agendas related to heightening tensions between the magical forces of Britain and France.
When Touma discovers something is amiss when searching for (what else) Index’s meal (we’ll never know—beef or fish?!) the flight crew arrests him lest a panic brew in the cabin. One of the terrorists then captures Index and tries to kill her, but Touma manages to rescue her. It’s a tense, claustrophobic situation and the flight crew seems ill-equipped to stop the terrorists, leaving it up to Touma.
On the ground in Britain, Laura Stuart and her logistics nuns represent at least one of the groups trying to bring the plane down (in her case, allowing it to land safely on a closed-off country highway). But their magical manipulation of the plane’s fuel gauges are overridden and the terrorist gets the pilot to regain altitude, so Laura has to switch to Plan S…for Stiyl Magnus, making his first appearance in the trequel.
Touma manages to track down the first terrorist and punches him out, but it isn’t long before he realizes there’s definitely a second, armed terrorist in the cargo hold. He uses hot tea to expand the ductwork so he can slip into the hold undetected, just like they do in the movies! Unfortunately the second terrorist is less of a pushover and has a grenade in his hand.
That’s when Stiyl arrives, perched atop a second plane below Air Bus 365. He uses his cards to neutralize the second terrorist, scolds Touma for not doing the bare minimum to protect Index, then departs as quickly as he arrived. Hi Stiyl, Bye Stiyl!
Air Bus 365 lands safely at Edinburgh; this is reported on the radio being listened to by what looks like another new group of magical users who are about to initiate a plan that will “break up the paradigm that is Britain,” suggesting they’ll be a key part of the complex magical conflict to unfold in this new arc, with Touma right in the middle of it.