Shokeisareta Shi ni Modori no Dai Roku Ouji wa Kokoku wo Sute, Ringoku no Guillotine Koujo to Fukushuu wo Chikau

Gustave is the sixth prince of a kingdom. He is supposed to marry into the enemy empire as the husband of Princess Abigail, draw out crucial intelligence from her, and thereby lead his own country to victory—becoming a great hero of the war. Instead, his kingdom betrays him. Gustave is executed—together with his wife Abigail, who is feared across nations as the “Guillotine Princess.” In the very next moment, Gustave opens his eyes to find that time has been rewound… back to six years earlier. In his second life, he vows to survive at all costs and utterly crush the homeland that betrayed him. To do so, the time‑reverted prince resolves to join forces with the Guillotine Princess herself.
Source: MU