@Kllick
As you said, the novel is still on-going, so there is very much still the possibility for romance (for either one or multiple girls, hence harem). I mean, while I love romantic development in stories and really don't like to see it baited only to not follow through (especially in a harem style), it's understandable why there wouldn't be any concrete progress yet. They are, after all, in the process of a war for the throne... romance can come later, unless a marriage would be of immediate political importance to their cause.
@Normalguy7
He literally explained in the chapter why he couldn't kill her (it would raise suspicion and he would be the prime suspect) or alter her memory (the magic being ineffective on memories with a large impact), did you even read the chapter properly?