These are pretty much just complimentary events for spending ingots I think. Since you get shurikens for every 10 you spend. And there isn't a daily limit on how many you can get. So it's like a free gift. F2P people get free stuff from it do just by doing dailies that gives them free shuriken. This isn't really a good even to just purely spend into by buying the shurikens. Unless you are using it to boost another event at the same time like Fukurokumaru Deals.