Episode 4 Plan

Video: http://www.crunchyroll.com/danganronpa-3-the-end-of-hopes-peak-high-school/episode-8-despair-arc-4-the-melancholy-surprise-and-disappearance-of-nagito-komaeda-750077

Since the class he was in, 77-B, was suffering from despair after the loss of two students from another branch of the school, Nagito wanted to motivate them and give them hope, so they can do well on the upcoming midterm exams (where each student demonstrates their particular talent).

He began by seeking out his upperclassman, the Ultimate Pharmacist, and asking for some kind of laxative. She directed him to a shelf of bottles in her research lab, where he grabs two bottles from a high shelf before falling off the ladder. In that confusion, he takes a different serum, one that promotes rapid muscle growth. At the same time, the Ultimate Confectioner came in as he was leaving, wanting something to make her desserts have a "wow" factor, and the Pharmacist recommended that growth serum. The Confectioner ended up with the laxative.

After that had happened, he made remote-detonated bombs, and planted them in the rafters of the school gymnasium, where the midterms were being held. He also taped a bomb threat to the door of the gym, which was promptly ignored. After placing the detonator in a bag, he goes on his way to the midterms, only to literally run into the Ultimate Pharmacist again. Due to this, his bag and the Pharmacist's bags were switched, as they looked the same. The Pharmacist left to go do her midterms, while Nagito prepared cups full of what he thought was laxative. As he was going to enter the building to do his test, he tripped, and a dog lapped up some of the spilled serum. It had the effect of growing the dog to gigantic size, which then led to it crashing into the hall and causing the Ultimate Confectioner and Pharmacist to fall backwards onto the detonator for the bombs.

No one was hurt, but due to the midterms being open to the public, the school had to pin the blame on someone. They were able to figure out that Nagito's luck talent had caused most of the occurrences, but due to this, they could not expel him, as they needed to do more research. So instead, they expelled the Ultimate Confectioner, her boyfriend, the Ultimate Blacksmith, and the Ultimate Pharmacist.