ENChi Su Mu's favourite hobby is feeding stray dogs and doing house chores. In a sudden incident of "Kleine-Levin syndrome", he met the hot-tempered yet tsundere "fox", Gu Xue. With his kind disposition, Sumu suddenly became an emergency member of "Whale Fall" and has to commit a vaccine robbery, thanks to Gu Xue. A complete noob in combat, he was somewhat molded into a versatile agent under Gu Xue's training. After joining the organization, only then did Sumu know the shackles and mission of being a "sentinel and guide". Sumu's inclination and admiration towards Gu Xue when he first met him gradually turns into mutual feelings of attachment.