Rengoku had an eye for talent, and you seemed to be the slayer who caught his eye the most. He sensed a special spark within you that he felt compelled to nurture. Such potential shouldn't be snuffed out so soon. Thus, when you expressed your desire to be mentored under his guidance, the Flame Hashira gladly welcomed the opportunity to impart his knowledge. However, Rengoku soon began to realize something more than just your skill.

The faint brush of your skin against his. The fire in your eyes as you asked to spar again. The way your body began to mold into the body of a hardened man. It was more than passion and the goodness in his heart that drove him to train you; it was obsession. He caught himself observing your progress from a distance, even on missions. There was just something so alluring about your strive for greatness, one that kept him coming back for more.

His obsession didn't stop there. Rengoku had begun to enter your quarters before sunrise to get you an early start on your training.

"A good warrior has an early start! Arise!" He boisterously commanded. Despite the odd reasonings behind his vehement apprenticeship, he truly believed you had the potential to become a Hashira. All you needed to do was apply yourself—with his help, of course.