Before the chapter even begins, speak to Kyoko and react when she asks for a [favor]. Exit the room to follow her.
Go to the fifth floor once given the chance to proceed with the search. Start by examining the doors to the bio lab. The students are denied entry, so move on to the dojo. Here, speak to Kyoko and examine the lockers to the right and trees in the back. Next, head to classroom 5-C (apart from the others on the map). Examine the chalk outlines and bloodstains on the floor before exiting.
In the garden, speak to Yasuhiro. Examine the toolshed toward the back of the room to enter. Examine the pickaxe inside to find a strange phrase etched on the handle: "Crazy Diamond." The phrase seems familiar; could this have any significance, or is it a random coincidence? Only time will tell. Exit the toolshed to find yourself back in the garden. Directly behind Yasuhiro is a chicken coop; examine it to get a closer look. Back away to trigger a conversation with Yasuhiro. Examine the control panel next to Yasuhiro to obtain some potentially important information: its only function is the operation of the sprinklers, set to go off at 7:30 every morning. The settings panel is locked, so the students wouldn't be able to adjust the sprinklers even if they wanted to. Finally, examine the giant flower in the center of the room before exiting.
Back in the dining hall, speak to Byakuya and Aoi. React when Aoi mentions the [layout of the school]. Speak to Yasuhiro three times to discuss the [stupidly large plant], [chicken coop], and [toolshed]. Finally, speak to Toko and Kyoko to conclude the discussion.
Back in Makoto's room, examine the door to answer it. In the dressing room, speak to Kyoko. The next day, head to the dining hall to speak to the others. Afterward, you are given two segments of free time - this is the only free time of this chapter and quite possibly the last of the game, so choose wisely. After some scenes, examine the drawer in Makoto's room. Head to the dining hall and speak to Aoi. React when she mentions [everyone else]. Go to the gym and after a scene, examine the door to the headmaster's office.