what is this anime???

fro what i remember its mostly about two teens, a male with black hair and female with blonde hair. they both were really good at using guns and i think they hated each other. i remember one episode where they were on a hijacked bus and the bus couldn't brake, they were also approaching a corner of the street so they used the ppl inside the bus to lean to one side and make the bus turn. i also think there was this one ep where they are on a plane and they find out someone betrayed them and that person ended up jumping out of the plane. i also think that they were being targeted by someone who would send out men in black to assassinate the two teens but the teens always manage to survive