Jelack

In a world where powerful beings are ranked by abilities, Key Academy is a battleground for the elite. Jelack, a mysterious new student, comes in as a bottom-tier Level D student. As students regularly spar to flaunt their powers, keeping her low rank a secret becomes increasingly difficult. Jelack trains in the shadows, aiming to rise above her D status. With unknown reasons for her transfer and her past shrouded in secrecy, she must uncover her true potential to survive the fierce hierarchy of the academy. Every day is a fight for recognition and respect, and Jelack is determined to prove her worth.

"If nobody notices that you are a girl until we graduate, I will give you a billion won.""I'm in."The bet was on. Will Shiru be able to hide her identity until she graduates?!Formerly hosted on Foxtoon, but can no longer be found on that site.Most sources for the series list 77 chapters, however, there are in fact 85 chapters total. Unfortunately, this includes the official English translation.