An action anime featuring guns about a boy and a girl who resolves a bus hijacking incident in one of the episodes
It sounds like Hidan no Aria (English title: Aria The Scarlet Ammo), except that the girl (Kanzaki H. Aria) has pink hair instead of blonde hair (her hair was originally blonde, though). Both of the protagonists are adept with guns, since they are students at Tokyo Butei High, where students are trained to become Butei (Armed Detective).

Episode 3 of the series features a bus hijacking incident, where the bus would be blown up if it were to slow down or stop. However, the part about leaning the bus with the weight of all the people on the bus does not occur in this series. Also, they were not stuck on the bus from the beginning, but they actually took on the mission to rescue everyone on the bus. They did get on the bus to search for the bomb, though.

The second half of episode 1 of the series features a scene where the two protagonists were inside a vaulting box inside a warehouse, when some remote controlled Segway mounted with guns came and shot at them. The male protagonist Tōyama Kinji (after activating Hysteria Mode, a special condition that runs in his family) shot into the muzzles of all the guns, causing all of them to explode.

Episode 4 and 5 is where the two protagonists found out that Mine Riko, one of their friends at school, was actually the culprit behind the previous incidents in episode 1 and 3. They had a few shootouts in the plane, and Riko escape from the plane by opening a hole on side of the plane with explosives and turning her clothes into a parachute.