Jeremy Heere is introduced as the 'loser' of the school, who has a crush on a girl named Christine Caniglia who doesn't even know he exists due to his social status in the school. So, he wants to become popular to get her to notice him. One of the ways of doing this is through joining the play that she is in.
Jeremy is told by one of the popular dudes, Rich Goranski, about a nano-computer in a pill called a 'SQUIP'. He wasn't too convinced at first but soon decided to give it a shot, getting the money to buy it off of a shady guy in the mall. He then takes it with his best friend Michael Mell by his side.
At first Jeremy believed that it didn't work, and that it was fake as he felt no different. But soon he started to hear a voice in his head which introduced itself as the SQUIP, who was going to help him become popular and get the girl. But first he had to get popular and so it proceeded to help him rise through the ranks of the school status.
The SQUIP gives him the idea to stop the whole play and confess how he felt to Christine while everyone was watching. Jeremy comes up with a whole speech and with no help from the SQUIP, goes through with the plan.
Christine gets angry with Jeremy for stopping the play, as she worked really hard and the whole play was ruined. Jeremy tries to explain the whole situation to her, but she refuses to listen and walks off.
The SQUIP offers that they write a book (Be More Chill) to explain to Christine the whole situation to Christine, using everything through the eyes of Jeremy and what the SQUIP has seen. Then it tells Jeremy to get rid of it, as it is not needed anymore.