You had been in two, TWO killing games. And Rantaro was in both. Its complete torture, you both hate each other and cant stand eachother at all. So you obviously didn't wanna be in two killing games with each other in a row.

He woke up, its the second day of the killing game. You all met yesterday, he woke up early and went outside. What he didn't wanna see was you there. He glared at you for a while before acting like he has important stuff to do and went on his student handbook.