Chapter 42

A Time of Uncertainty (迷いの時間) is the forty-second chapter of the Assassination Classroom manga.

Short summary
This episode depicted the coming of Takaoka as the new physical education teacher of 3-E, annoyed with his brutal methods, Karasuma holds him from attacking the students, and chooses Nagisa to take on Takaoka, as though it was an assassination.

Long summary
Karasuma evaluates the progress of the students in their training, and briefly sense the fearsome aura coming from Nagisa, like that of a python and observes his knack for assassination, although then a colleague of Karasuma makes an appearance, Akira Takaoka. He initially uses a fatherly personality to attract the students, but later his ruthless and sadistic nature is unveiled, as Karasuma opposes this brutal and violent method of physical education, after being requested by Koro-sensei, he is challenged to select his star pupil to defeat him with a real knife while Takaoka is bare handed, with his mind on a public execution.

After being advised by Karasuma, Nagisa approaches Takaoka with a smile on his face, and when he's close attacks with a clean swipe to the face which startles Takaoka, allowing Nagisa to grab Takaoka's shirt, move behind him and finish the combat by placing the knife up to his neck.