Girls, especially Japanese girls, are often very timid and reserved in relationships. They often won’t say what they really think, and will bow down to what you want to do. It can be how you spend your evening, or where you’re gonna go to for a day together. Provided they don’t actively not want to do something, they will generally say yes if you suggest doing it. If they know that it’s something you like doing, they’ll often act like they enjoy it and are eager to do it, even if they don’t/aren’t.
This is a good thing, and shows that a girl cares about you and is willing to sacrifice for you. Over time, it can wear at her though, especially if you are ignorant to her sacrifice (as she acts like she genuinely enjoy things, it can be very hard to tell when she doesn’t). It is something you should be aware of, and actively look for.
Men on the other hand, tend to whinge and moan if they’re doing something they don’t particularly enjoy, even if the girl enjoys it. Just the occasional little hint that you’d rather be somewhere else doing something else will anger her if she’s enjoying it, and this is especially the case if she sacrifices for you. Even though she’s essentially pretending that she likes what you like, and you are innocently unaware of this reality, if you whinge at all or even just look like you’re not enjoying yourself, she will get upset. She can then get angry with you, and you not understanding why, and thinking she is being unreasonable will make it even worse.
My advice? Balance the scales a bit. When you have a day together, ask her what she wants to do, without suggesting anything yourself. Try to seem enthusiastic and eager to do what she says, even if you are not. Then when you are doing whatever it may be with her, try to be (or at least seem) happy, and do not give any hint at all that you would rather be doing something else. This is difficult, but just keep reminding yourself that she does this for you, probably a lot more often. Mutual sacrifice leads to much stronger, longer, and most importantly, happier relationships.