A really solid manga, I'm hooked and craving for more chapters.
Don't worry about the ending from the first chapter, it's author's way to keep readers attention and give us some plots for future chapters to deepen the relationship with each girl (I mean the dude gotta keep his readers intrigued for the upcoming chapters or else his manga will get low sales and get axed), after the first chapter we see that the girls themselves aren't really mad at the MC and they're very nice girls and charming with their own quirks/personalities.
Btw I hope this series ends in harem ending, I mean, there's a few points that makes me believe this will be a harem ending:
1 - its medieval times and usually harem set in those times are sure to give us harem ending (dunno if it's a 100% of the cases),
2 - the princesses have a healthy relationship with eachother and don't seem to be plotting or backstabbing for the position of future queen, and I bet they'd rather live together than being married to other kingdoms while the first princess inherit the throne (unless she reliquishes the throne in consideration for the third princess who will 100% chance be the winner if this manga ends in a monogamous ending).
3 - the dude on top of being a prince (being royalty and all that stuff) also singlehandedly saved their kingdom and is risking his life to save the kingdom from the a future invasion, therefore he's more than worthy to be the future king and marry the girls,
4 - by the way the pricesses looks are so different appearance-wise makes me think that either the king has more than one wife or else his genes or the queen's are very mixed from their ancestors who probably had more than one of wives, thus setting a precedent.
5 - he already kissed all the girls and is kissing them again in the later chapters
6 - also there's a page in the first chapter that shows all the princesses sleeping and the bed has 8 pillows, so it's probably a foreshadowing of him sleeping with all of them when they marry