Wow! This is a cute and smart toy. You can actually play koto on your iPhone and iPad. 

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It comes with the basic sets of tuning. You can also save your own tuning.

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Under the setting menu, there are oshide, hikiiro, pizziacato and sukuizume. You can even tilt the koto to get a comfortable angle to play with. You can also record while you play.

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You can download it from App Store. It's not free but very useful for a reasonable price. Not as good as the Apple version but there's a Galaxy version, too.