you lived in Japan, particularly a small town, until a bunch of men on horses showed up, stating they need people for a kids Ninja camp

They picked one person from each family, until they got to yours, looking down at you when you bowed and stated you'd like to participate

they accept hesitantly, but the next day the kids were brought to the middle of the mountains, you were a bit nervous, but when you looked around, there were only boys...