The Japanese just have a lot of weird ideas when it comes to sex. I say "weird" - they're weird to us, I'm sure it's perfectly normal to them. Now some of this is learned through osmosis through lots of the porn stuff, so I'm sure some of it has to be taken with a grain of salt. But there are a few other odd things too, that I'm certain are something that actually happen at some reasonable rate.
I remember reading an AMA on Reddit, and the celebs in question were three Japanese porn stars - I forget the names. One of the questions was from an American who had lived in Japan for a while. One time, he was having sex with a Japanese woman, and while it was going on, she said "stop". To any westerner, this is an obvious sign to stop, see if something's wrong, did you hurt them, etc. And that's exactly what he did. But she really didn't want him to stop. But she was almost acting like it. He was asking if this was a common thing in Japan.
Turns out it's relatively common. I forget the exact answer now, and I'm actually super-interested, so I want to go back and look for it later, but it's kind of a strange thing.
This is from an eroge game I play called Sengoku Rance. The game is honestly an excellent strategy/RPG/Visual Novel game, regardless of the adult content.
In the screenshot, you can see the titular Rance character, who's completely obsessed with sex. His primary motivation for going to Japan (where this game takes place), was simple, and explained very early on - "I heard Kouhime of Owari is beautiful. So I came to fuck her." Further, one of the game's objectives, which grants you ten points if you finish it, is to fuck 300 women. Even further, Rance has a "satisfaction" mechanic that allows you to unlock bonuses for every ten points you get. The primary method of increasing this is through having sex, as, generally speaking, each new woman you have sex with will increase satisfaction by 5. Other things can do it too, but sex is your main way of increasing it. I say all this just to give you an idea of the kind of guy he is, and what kind of game this is. But again, even if you stripped all the adult stuff, it's an excellent game regardless.
In this scene, he's going to visit Senhime, a commander in his army. He's been trying to have sex with her for a while by now, but she's completely uninterested, and only interested in fighting in battle. This is just one of Rance's ploys to get her to sleep with him. I mostly posted it because it's ridiculous logic. "No" suddenly becomes "Yes" because it's night?
This is just another strange Japanese way of thinking about sex (the game's publisher is a Japanese company), that just doesn't compute to most westerners.
EDIT: This is an apt picture describing what you think it is, and what it actually is.. Only it's still better than Shogun 2, because of additional elements. Much as I like Creative Assembly, AliceSoft wins this round.