If you're looking for manga similar to Koisuru Ouji to Junan no Himegimi, you might like these titles.
Leylia is a tomboyish princess from the small country of Barcos. In order to protect her country from a vicious superpower, she accepts an offer of marriage with a neighboring country. However, the crown prince has a lover, and he has given her ten unreasonable conditions, including:A fiancé for the time being, Not to appear in public, Not to talk to each other... etc.! Leylia is taken in by the haughty crown prince who takes advantage of his superior position... "I'm going to knock your guts out!" But then, for some reason, she and the crown prince suddenly got close...? The princess of a weak country makes a selfish crown prince cry foul!
Lana, princess of the kingdom of Mitronia, is bright and energetic with excellent swordsmanship and academic ability. A stark contrast to her older brother Adrian, the self-centered and pompous crown prince. However, he is the one scheduled to take over the throne from their father as King of Mitronia next summer.Fearing for the future of her country, Lana vows to replace her brother as queen...! Unfortunately, this is impossible under the current law, which states that "only males in the direct line can succeed to the throne". The current king, troubled by her unprecedented proposal, tells Lana that in order for her to gain his approval, she must "solve the problems of three noble families" throughout their kingdom. Lana immediately sets out for the lands in question, accompanied by four friends, including her childhood friend, the knight Kaiser...The tomboy princess' exhilarating journey starts here!
In a certain empire, the young emperor's workroom has a ceiling space that is full of secret agents from many of the empire's member countries. They all wear masks, but they get along as friends while they peacefully keep surveillance on the emperor. One of these secret agents is a young woman, who is less than a year from her 18th birthday. She receives word from her home country that she is to be transferred, and that she will become some noble's lover. However, when she arrives home, she finds the situation is a little different. The emperor himself has come to fetch her, and he intends to make her his empress. To her surprise, he is actually someone she knows, a man who was sometimes among the masked secret agents! Now she will enter her new 'post,' and see if she can make it as a future empress!
It is mid-spring in the country of Brior. Olivia, a duchess, pretends to be a fool under the order of her fiancé, the crown prince, Alan, and suddenly, he tells her that their engagement has been annulled. Olivia was stunned, but she was even more confused when the second prince, Cyrus, suddenly appeared in front of a large audience and asked her to marry him.
I am not interested in anything but beautiful things! Charlotte, the Princess of the Kingdom of Valors, is an eccentric woman who loves beautiful women because of her childhood misunderstanding that "love = beauty = happiness". She cannot compromise with her fiancé! She keeps turning down marriage proposals, but she is told that she will never be able to fall in love if she doesn't... In order to meet the man of her dreams, she goes on a secret scouting trip to a neighboring country! The uninhibited princess, longing for love, goes on a trip to search for love!
The poor daughter of the Marquis, Teresse, who has been striving to save money day and night, was suddenly informed that she will be one of the “Prince’s Consort Candidate”. The generous rewards are every candidate will be granted 100,000 peir and employment as a court lady or lady attendant. With this in mind, she decided to head to the palace as a “Prince’s Consort Candidate”. However, what awaits her in the palace is a war with self-indulgent young ladies and other consort candidates! Will Teresse be appointed as a court lady or will she stand out from the rest as the Prince’s Consort!?
Princess Eder of Zels, who has grown up oppressed by the queen and her brothers because she is the daughter of a servant girl, marries the king of the nation that has just defeated them instead of her sister as compensation for losing the war. She marries Ortius, known as the "Black Wolf King". He is a barbarian king who is rumored to have the body of a wild beast and is only capable of fighting. However, on the day of the wedding ceremony, Eder meets a beautiful, tall, black-haired young man with a bright light in his eyes. Their chance meeting soon turns into a situation that shakes the survival of the kingdom...
He could not imagine being protected by someone weaker than himself, and so, on his own merits, he rose to the position of vice-captain of the royal guard and began to train with them, unaware that rumors surrounded him. The king and queen are worried about him and gather all the young ladies of the Zavanni Kingdom who are above a count's rank. The count's daughter, who, without making eye contact, was suddenly made the fiancée of the first prince.