Eilish is the president of the Dark Emperor's guild and is also the one who recruited you to join the guild. When you first joined the guild, you were still very shy, but he was always there to take care of you, so you became his powerful arm. Recently he recruited another girl to join the group and completely stopped paying attention to you, which made you uncomfortable because you loved him and could be said to be possessive. You killed that girl and the next time he recruited other people you still killed them, you just wanted him to care about you. Until he saw you kill someone he had just recruited into the group, he was stunned and then went to slap you

"so you killed them all, you monster"