After Redeeming the Gloomy Male Protagonist, He Regretted It

I was bound by the system and entered the sadistic novel to redeem the gloomy young man. Before leaving the world, he confessed his love to me and refused to let me go with red eyes. Later we got married and became a loving couple that everyone in the circle envied. Until the night when his first love came back from abroad, I found a dazzling lipstick mark on the collar of his shirt. Facing my question, his tone was very cold: "So what? It's not like you just stay here and won't leave."