source: Starpuck: Gif it my all, anime win! - Page 4 - Assassins - Nerd Fitness Rebellion

run off(→ run something off) = run away

informal leave one's home or current partner in order to establish a relationship with someone else:

家出する; 【人と】駆け落ちする(together) «with»

e.g. he ran off with his wife's best friend