Koikishi Purely Kiss the Animation (2013)

When they were kids, Kaname and Erushia were once trapped in a building where a fire had broken out. Erushia got stuck under rubble, but Kaname didn't plan to give up on her, even though the situation seemed hopeless. Just as Kaname was about to run out of strength, a modern-day knight saved them. After the incident, the two promised each other to become knights and protect justice and righteousness better than anyone else. Years later, they fulfill their promise and work side by side to protect and uphold justice, while love starts growing in their hearts.