Isekai Saikyou no Yome desu ga, Yoru no Tatakai wa Ore no Hou ga Tsuyoi You desu - Chiryaku wo Ikashite Nariagaru Harem Senki

Albert is reborn in another world and strives for a peaceful life in the Kingdom of Alexa. However, after being "kidnapped" by a Demon Goddess of war, Marida, he becomes a wanted man by the Kingdom! Unable to return to his original country, Albert decides to live in the Empire of Eranzia. While enjoying intimate moments with the alluring body of Marida (but not just her!), he uses his previous worlds knowledge to achieve great accomplishments in governance, military affairs, strategy and of course... Night-time battles!