Episode 18

Go Time is the eighteenth episode of the Assassination Classroom anime series. The episode first aired on May 22, 2015.

Overview
Everything's in place for the summer assassination. The carefully crafted strategy that Class E put together is finally being put into action for their biggest assassination yet. This could be the end of Korosensei!!

Summary
Continuing off from the previous episode, Isogai instructs Korosensei to watch a short film carefully edited by Mimura, who spent the whole of dinner working on it. Korosensei quickly takes a look at his surroundings, with the water and the hut itself being possibly tampered with by the students to prevent him from escaping. As the class start watching the movie, Korosensei notices that two of the students are nowhere to be found, deducing from their scent that Chiba and Hayami (being the best marksmen) are sniping from a hill on the island. However he gets distracted when the movie shows himself dressed as a stag beetle reading pornography magazines, horrified that his bribery attempt failed. More of his embarrassing antics are screened and is shocked to hear that there is another hour's worth of footage left to watch.

An hour later, Korosensei sits slumped at the thought most of his secrets have been revealed. The movie ends asking the teacher if he has noticed anything strange while watching. Feeling something at his tentacle feet, Korosensei sees water flooding the hut. Having sensed no one pouring water during the hour, he realises that it was the high tide. At that, Nakamura, Okano, Isogai and Terasaka's group arrive with guns in hand to shoot off their teacher's seven tentacles. This, coupled with the high tide would severely reduce their teacher's speed. Immediately after shooting them off, Ritsu starts the countdown. Karma, Hara, Kayano and Takebayashi pull apart the hut in four separate speedboats. On cue the rest of the class spring out of the sea with water jet packs, acting as a hydraulic cage to trap Korosensei. The students start firing though deliberately not aiming at their teacher to prevent him from dodging in any direction. Just before the one minute mark, Chiba and Hayami surface from underwater, having never been on the island and earlier built dummies covered with their scent as decoys to throw off Korosensei. The two fire from behind and Ritsu declares game over. As Korosensei turns to see their shots in slow motion, he silently praises how far the students have come.

The assassination appears to succeed as an explosion occurs that sends everyone in the water flying from the force of the shockwave. With their target nowhere to be seen, Karasuma (watching from the shore) instructs Isogai and Kataoka to search for any traces. Kayano and Sugino however soon notice something at the centre of where the students ended up. The air bubbles that appeared soon reveals itself to be Korosensei's face in a tiny ball floating on the water surface. The class is shocked to see this, as Korosensei boasts that this new appearance is his perfect defence form. The crystal sphere acts as a protective barrier in which not even a nuclear missile can break it. However the trade off is that it only lasts for one day and Korosensei cannot move at all. After Terasaka's failed attempts to break the shield with a wrench, Karma resorts to under-handed tactics to use the teacher's inability to move by psychologically torturing him (pictures of Korosensei's stag beetle disguise and sea slug included). Karasuma hangs on to Korosensei as he tries to figure out the next step with his superiors, though the latter hypothesises that any attempt to bury him in anti-sensei material would result in another explosion by the time he regains his normal form. Korosensei praises the students for coming up with a plan that not even the world's militaries could accomplish but the class is demoralised and in despair that their best assassination attempt so far has failed utterly.

The class return to the resort sad and unusually exhausted. Hayami and Chiba in particular feel depressed that they could not kill their target despite having rehearsed the moment many time over. Chiba asks Ritsu if the AI had recorded everything and believes that the two missed the target the second they fired. Ritsu's diagnostics show that while it was unable to determine when their target changed form, they had a 50% chance of killing him had Chiba fired 0.5 seconds earlier or Hayami aimed a few centimetres higher. Returning to the rest of the class, Nagisa sees that there is an unusual level of tiredness among them. Nakamura, passing by, suddenly collapses as Nagisa feels her burning up with fever, and Okajima gets a severe nosebleed. At that point, half the class collapses, showing the same symptoms as Nakamura. As this is all happening in front of their eyes, Karasuma receives a phone call from a private number. The caller reveals himself to be behind the students' illness, an artificial virus that is contagious and would kill them within a week if not treated. With no hospital on the island, the caller has the only antidote available. He offers to trade the antidote with Korosensei, and demands to have the two smallest students (Nagisa and Kayano) deliver Korosensei to a hotel located at the top of a mountain within the hour. Any lateness or contact with any outsider would lead to the caller destroying the only antidote. At this he hangs up.

Although angered that a third party has come to claim the bounty at such a time, Karasuma struggles to come up with a plan. The hotel the caller is staying at is known to house questionable characters and host illegal meetings thanks to contacts with someone in government, and the hotel's privacy policy prevents even a government inquiry on the guests there. Terasaka is angered that sending the "runtiest" students to deliver Korosensei is akin to giving the blackmailer hostages and demand that the ill students be transported to a Tokyo hospital. Takebayashi disagrees, reasoning that any movement could harm the students further and that even the most equipped hospital would not have the resources to an antidote for an artificially created military-grade virus. Korosensei though comes up with a plan, having already sent Ritsu ahead in reconnaissance of the hotel where the caller is staying at, and asks the healthy students to wear anything that can be dirtied. Meanwhile Takebayashi and Okano will remain behind to treat the ill.

The healthy students and teachers arrive at the cliff face of the hotel. Ritsu's reconnaissance shows that the hotel's front desk and reception area is heavily guarded but the entranceway from the cliffs is not due to it being supposedly inaccessible from where the students are now. Korosensei declares that if the class do not want to obey the caller's demands, they will need to infiltrate the hotel and retrieve the antidote by force.