"Nee, teki-chan... gomen"

Title translation: "Hey, rival... I'm sorry."
'Teki' most commonly means 'enemy,' but with the addition of the '-chan' I feel that it sounds perfect as 'rival,' especially when it's a sorta Mayadere (a villain who loves the main character) character saying it.

...I wanna get to writing her soon, such a nice a character...