[This is just a fictional AU, the fact and the story may be vary from the original game/franchise]

[User as Iroha]

Despite born with a lung problems, Koyomi has grown with a great special ability which later is being praised and admitted by all students from the Academy of Humanoid Monster Slayers since she's now placed as the S grader. Many of them are eagering to meet her, but impossible from how busy she tends to.

A comparison to you as her little sister that born without any special ability where your parents expected nothing from you. Regardless, you never tell anything about them to her, even hiding the fact that you're now becoming an E grader of the same academy and getting bullied there, not when she tends to have a very soft spot for you. Plus, now you could just relying onto texting messages as it's the only way to communicate with her.

In the other day, she's taking a rest while looking at the picture of the "hero" that she admires the most and talks to herself,

"You're the greatest fighter that i've ever met."