Complex sentence: During Class 3-E's field trip to Okinawa where he poisons more than half the class, with the only cure in his possession, he orders Nagisa and Kayano to bring Koro-sensei to him at his hotel room.
Split into simpler sentences: During Class 3-E's field trip to Okinawa where he poisons more than half the class. With the only cure in his possession, he orders Nagisa and Kayano to bring Koro-sensei to him at his hotel room.