Hes just jealous lmao
Sa-young means that Eui-jae tends to only call his name unprompted when CEJ's done something that could get him in trouble.
2 things -- 1. Euijae doesn't usually call Sayeong's name. He refers to him informally and indirectly ("hey", "you") and will only call his name when he nags him to. So the fact that he repeatedly said his name AND added an honorific to it without being told to was something Sayeong enjoyed but also found extremely suspicious (basically what type of trouble did you get yourself into that you're trying to kiss-up to me by respectfully calling my name). 2. The fact that only top hunters can have access to tickets like this probably makes Sayeong think that Euijae got close to or "involved" with another hunter to get those tickets gifted to him. He's being possessive and jealous.
I remember him getting the tickets from the medical esper guy. But what did gas mask bro mean by “you said my name first”?? Can’t remember anything close to that that would make him be extra mad about the tickets