Sayonara Zetsubou Sensei S01 E01 Sayonara, Zetsubou-Sensei

Kafuka Fuura is cheerily walking to school one April morning when she suddenly spots a man trying to hang himself in a fit of despair. Kafuka manages to use her weight to snap the rope, thus saving his life. Nozomu Itoshiki, the man, eventually cannot take anymore of the girl's ridiculous ramblings, and runs off to school to start homeroom at the beginning of a new school year. When Nozomu walks in the door, he finds Kafuka is one of his students.