He Kneels At My Grave Regretting Everything

Dawn goddess Etherea saves war god Dorian in battle millennium ago, but rival Velta steals rescue credit. She begs her father to arrange marriage saving his life, enduring century of cruelty as he favors Velta. Etherea sacrifices herself sealing the demon lord, dying unforgiving; Dorian kills Velta when truth emerges, dying of regret at her grave.