On this episode, the class attempts to assassinate Koro-sensei at the island resort. Later, a flash back reveals the class training and making their plans for the island.
The class is really going all out for this attempt which is interesting but will fail as usual (since it's sadly predictable because the series is not close to the finale which is around 22 episodes in total). Although it's nice that they made the plot exciting just like the previous ones. Anyway, I can't wait to see the next episode to be action packed. Now what will Koro-sensei do to counter his students' tactics? Overall, another cool plot development.
Conclusion: Another cool plot development.