Classification

Apparently, Master Reina took her duties of teaching him seriously. She put on a pair of spectacles, changing into a more formal attire while taking Rui to a classroom set-up.

"Now then," She remarked, pushing up her spectacles. "Let us begin. Please begin noting."

"I'll be fine."

"Very well, but I will not be pleased if you are unable to follow." She told him with an officious tone.

Rui sighed. "Do you really need to do all this?" 

"What are you saying? I take my duties as a teacher very seriously!" She insisted, pushing up her spectacles.

"Right."

"Now then... What is assassination?" She asked, writing the word 'assassination' on the board.

"The field of killing."

"Very good." She nodded, drawing an arrow before writing down his response. "Now what is an assassination?"

"Any intended elimination of a target," Rui replied.