The Future King's Pregnant Mistress

Emily has been living with Marco Fierezza for three years. One day, she discovers that her businessman boyfriend is actually the crown prince of Niroli! Called back to Niroli, Marco, who has his own ideas for the kingdom, argues against his grandfather's focus on tourism. Old traditions get in the way of the growing feelings between Emily and Marco, and life gets even trickier when Emily discovers she's pregnant with Marco's child!

Part of the Niroli Rules series (ニローリ・ルールズシリーズ), also called "The Royal House of Niroli" series, which goes as follows:

1. Itsuwari no Kamen
2. Doctor wa Prince
3. Prince to Scandal
4. Chichuukai o Wataru Kaze
5. Tsumetai Prince
6. Kokoro no Symphony
7. Yuuwaku no Perfume
8. Oujo no Unmei