The Day We Swore to Heaven (天を契んだ日, Ten o chiginda hi) is the first episode of Maken-Ki!

Haruko Amaya arrives early to accompany her childhood friend Takeru Ooyama on his first day at Tenbi Academy. After she excuses herself to prepare for the induction ceremony, Takeru wanders around to take in the view, and witnesses a curious confrontation between two female students before having a run-in with Kodama Himegami. At the ceremony, Takeru learns that fighting is a way of life for the students. Kodoma requests a duel with her enemy Takeru, intending to kill him, but their match is interrupted by Inaho Kushiya who claims to be his fiancée. Takeru ends up sharing a dorm with Haruko, Kodama and Inaho..