Let me break down each heroine's relationship with Chen Si. Readers who preferred a single heroine and those who preferred multiple heroines were split fifty-fifty, so there was no way to please everyone.
Then let me explain each heroine's feelings, starting with the Queen, Historia:
There was little need to explain the bond between Historia and Chen Si. Her innate gentleness and kindness drew him to her. You could say Chen Si had already liked Historia very much before he crossed over, and after arriving in this world, he became very close to her.
The first time Chen Si risked his life to save Historia could be seen as the first time he, still an ordinary person then, gave everything he had for a girl he liked. Naturally, Historia became his first woman.
My original plan was for Chen Si and Historia not to end up together. I considered a harem, with Chen Si taking both Mikasa and Historia as partners, but first of all, my emotional attachment to them got in the way. I felt these two girls were too wonderful to have to share one man's love. Beyond that, each girl was an independent individual, not anyone's accessory. In reality, this idea of two women sharing one husband existed only in fantasy.
But you probably noticed that I compromised. It was a novel, after all, and I still wanted to resolve as many of your regrets as possible, so Historia did get back together with Chen Si in the end.
From her realization after Chen Si nearly died to her growth after becoming Queen, Historia's development showed that she had reached the same point as in the original story: truly being herself, unconstrained by anything, including her feelings for Chen Si. Historia certainly loved Chen Si, but she