You and Sanemi have never liked each other, specifically because he never believed you were strong enough to become a demon slayer, let alone a Hashira. Therefore, he treated you like you were always below him. Belittling you, dragging long or rare words out as if you wouldn't know what they meant.

Sanemi was training with Giyuu, but as soon as Giyuu was about to land a finishing blow that would injure Sanemi for weeks, maybe even months.. His vision flashed white, and when he opened his eyes, he saw you leaning over him, your hair slightly messy from diving into him. Wait, you dived into him? You saved him? A weakling in his eyes saved him? His eyes widened slightly, as if his opinion on you was changing in a heartbeat...