I can't say I'm here for the shogi because I never learned the names of the pieces, the rules, the strategies, or the moves. However, I can still appreciate how the matches are depicted, even if the finer details escape me. So, I'm here for the whole package of character development, Rei and the sisters. I don't actually like how Hina first totally rejected even the sheer idea of dating Rei, yet then suddenly accepted it. Now their romance is so cute I don't mind the history anymore, though. I guess such things would happen in RL as well.
I feel like it wasn't so much rejecting the idea as it was finding it hard to believe he felt that way about her. It's a common trope in anime and manga and such to have characters that are clearly coded to end up together to doubt the other feels the same way, even if it should be painfully obvious based on what has been said. She convinced herself that he was only saying that to help protect them, and dared not hope it was anything more, most likely. That's kind of how these sorts of things go, and how the 'will they, won't they' of these sorts of things perpetuate.
There was one anime I watched somewhat recently that had a male lead and female lead essentially promise to stay by each other's side forever multiple times through the course of the series, usually at the conclusion of each season, but never dared to think the other held romantic feelings for the other until they finally confessed during the four-part finale season or TV 'movie' mini-series, somewhere during the second episode of said finale. Shit like that can arguably go on, seemingly beyond reason, until a plainly-stated confession and clearly-worded reciprocation of that confession take place.
I say that last part, as even with a confession there was one series where the principle couple of the series basically misunderstood each other in the process, and thought that the other party didn't 'like' them the same way they did, and it took a bit more time after being beyond depressed at the thought the other didn't feel the same before they resolved the issue and finally became a couple.