Do you guys know the name of the flute used for Yasuo's login theme?

I asked Riot, but even the company doesn't know who composed it nor do they know the name of the instrument. I checked almost every website I could and I even listened to the types of flutes mentioned, but I haven't found it because none of it sounds right. Some say it's the traditional bamboo flute (which also has a very beautiful sound, but it doesn't seem like it fits that one and some say it's the shakuhachi which didn't match the sound either). Please, anyone of you who may know, please, please, PLEASE let me know because I am in love with it and I am sort of tired of repeating the same melody for a week or two almost now. Thank you. (Even the wiki pages are not confirming it, there's always a "probably ________" or "it may be the ________") .