WakeAtNite

If this is long story...he will get engaged to other woman and keep having s3x with Grace until she suddenly pregnant and run away. The misunderstand continue until he realised something...truth about her family rebellion was clear up and time skip, meet again with her having child + start chasing arc/redemption arc

The ending feel bittersweet. Usually we see a happy end manhwa where they live together happily but this seems quite realistic.