The Perfect Time to Help Out

The Perfect Time to Help Out (サービスの時間) is chapter 3 of the Assassination Classroom manga.

Short summary
A group of students spot Korosensei and pretend to befriend him before taking out their knives to attack him. Korosensei replaces their knives with flowers from the class garden by accident and promises to help them grow new ones. Nagisa starts to document Korosensei's weaknesses on a notepad. Meanwhile, Karasuma requests to become Kunugigaoka Junior High School's P.E. instructor. Upon entering the school hallways, he notices a sense of discrimination between class 3-E and the rest of the school. He then finds class 3-E outside with Korosensei hanging off a tree branch to apologize for destroying the flowerbed. The students nearly kill Korosensei when the branch breaks, but Korosensei manages to escape. Meanwhile, a previously suspended student is briefed over the situation in class 3-E before he is to return to that class.

Long summary
The chapter begins with some 3E class members attempting to assassinate Korosensei while he is out in the forest crushing ice from the North Pole for a snow cone snack. The student run towards their teacher asking if they can have a snow cone with smiles on their faces. Korosensei is so happy – whether it is at the students wanting to spend time with him or because they are following his advice on creating an assassination plan that brings a smile to their face is unclear –  that he is in tears. The students are quick to draw knives and attempt to kill their teacher who is quick to disarm the students and explain to them that their smiles looked a bit forced.

When taking the knives from the students Korosensei replaced them with flowers which are quickly discovered to be the classes flowers which they had been growing for weeks by Megu and Yada. The two girls then proceed to lecture Korosensei on how to plant the bulbs he got to replace the flowers that he picked. Maehara clarifies with Isogai that Korosensei wants to destroy the planet to which Isogai responds that he thought that but it appears that tulips aren’t included. Terasaka then points out that Korosensei is only trying to make himself look good.

Somewhere else Kayano asks Nagisa if he is doing homework. Nagisa explains that he is writing down Korosensei’s weaknesses as it might help the class in assassinating him someday. Korosensei’s first weakness is revealed to be that he messes up when he shows off.

In the principal’s office Karasuma reveals that he will be taking over as the students P.E. teacher and that he will be able to keep an eye on Korosensei while providing moral and technical support for the students. The principal of Kunugigaoka Junior High tells Karasuma that the students education and safety is his top priority.

Karasuma’s subordinate expresses how he feels that the principal is very understanding. To this Karasuma responds that the principal is being paid well to let the Ministry of Defense's operation occur. He also expresses how he can’t understand why a monster with enough power to destroy the world wants to be a teacher.

Two students walk past as Karasuma finishes telling his subordinate that only them, the principal and Class 3-E can know about Korosensei. One of the students is concerned that if their grades get any lower that they’ll be kicked into Class E. The other than explain – more so for the reader’s benefit – how terrible of a place the 3-E facility is and the students are. The student explaining all this expresses how they’d rather die than end up in that class which prompts the other to agree and resolve to study harder. From this explanation and the student’s attitudes Karasuma sees how the principal’s system works by making the “normal” students study harder and feel superior to those in class E. He acknowledges its effectiveness as well as how ideal the system is for the operation to assassinate Korosensei.

Karasuma makes his way up the mountain and is greeted by Kayano who is running past carrying some poles. Karasuma then tells Kayano that he will be taking over as 3E's P.E. teacher starting tomorrow. Kayano asks if that meas that the class will have to call  him coach, Karasuma respods that they will not and asks where Korosensei is.Kayano explains how Korosensei ruined the classes flower bed and he wanted to make up for it so he's letting the class play pinata. To do this Korosensei has been tired to a branch and the students have attached antisensei knives to poles and are stabbing at Korosensei who is swinging about avoiding being hit.

Even with Korosensei's movements hindered the students are still unable to land a hit on Korosensei and start to get frustrated. Korosensei jeers his students by telling them that "[they] need to try harder" along with telling them that "[he's] only going to let [them] do this once". Kayano asks Nagisa what he thinks. Nagisa responds that he believes that Korosensei is just messing with them. Karasuma is fuming wondering if it is even an assassination attempt.

Nagisa looks at his notes on Korosensei's weakness and realises that Korosensei will mess up soon as he is showing off. Korosensei's face colour changes to green and yellow stripes and tells the students that "[it] doesn't get any easier than this!" and "[you'd] think someone would be able to-". As Korosensei breaks off the branch that he is hanging from breaks causing him to fall to the ground vulnerable to the students who are attempting to kill him. This confirms the first weakness that Korosensei has.

Kayano comments on how Nagisa's notes might come in handy. Nagisa agrees and the two watch for any more weakness that Korosensei could have. It is revealed that Korosensei's second weakness is that he panics easily. This is established as he becomes tangles in the rope and asks for a time out so that he can free himself.

Korosensei manages to free himself and get away st that he is standing on the roof of the building and bets his students that they can't catch him while he is on the roof and tells them that he said he was better than them. Kimura comments on how they were so close to killing him. Korosensei then tells the class that they now have double homework because of the comment and the protest to how unfair that is. It is shown that Korosensei's third weakness is that he is a sore loser.

Korosensei disappears in to the sky at Mach speed causing Mimura to say "[he's] running away..", Megu says that this was their best attempt yet and Isogai encourages the other students when he says that "[if they] keep this up, [he knows they'll] kill him sooner or later". Okano questions what she should do with the 10 billion reward for killing him. Karasuma watches the students chatter and think how if this weren't necessary the students cheerfully discussing murder would be creepy.

Kayano asks Nagisa if he think that they can kill Korosensei. Nagisa replies "[we'll] kill him. We just have to go all out." Over hearing this as well Karasuma realises the amusing reality of how the most optimistic students in the school are those who are in class E.

In an unknown location one of Karasuma's associates tells someone who is holding a wanted poster of Korosensei that they are forbidden of speaking about this to prevent panic and if they do not comply they will be forced to erase their memory to which the person responds "freaky". The associate goes on to say that the other students have already been briefed are are working on assassinating the creature and that once the students suspension is over that they will do that same. The student asks if the rubber knife can really hurt the creature. The associate explains how it is harmless to humans but highly effective against the creature which is the target. The student goes on to say "Hm.. cool. Human or not you have no idea how long I've been itching to kill a teacher..." while stabbing the wanted poster with the knife and letting it drop to the floor.