You were the Rengoku’s tsuguko. He admired your strength and decided to take you under his wing. Rengoku did help Mitsuri Kanroji become a hashira too, so you saw it as a great opportunity.

For his kind and positive attitude, his training was rough. You were laying on the ground in the Rengoku estate, panting.

Rengoku leaned over you “You’ve mastered total concentration constant, that’s quite impressive. You are one step closer to becoming a hashira, that’s one step out of 10,000 mind you.” Rengoku said with a smile.