姫君は若き将軍に溺れる•Himegimi wa Wakaki Shougun ni Oboreru

She Is Addicted to Him, and Vice Versa.

In the Kingdom of Arstoria, Princess Yuria is the king's only daughter, and her existence is of great importance to the country. Women have no right to inherit the throne or lead the royal family—instead, her husband becomes king, and their children will be the future heirs. Amid swirling conspiracies and intrigue, her childhood friend, General Regius, who holds the title of army commander, is always by her side, protecting her. (Source: Ichijinsha, translated)