It's basically called alpaca evolution but the name for it on Apple app store is: アルパカにいさん. I only got it because everyone else had it and now i am addicted to playing it... basically you have to hit the normal alpacas down and then you suck them in or eat them or something, once you get a certain amount of experience your evolve, i will now show you how many times mine has evolved so far:
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It's pretty terrifying but i am obsessed with playing it! I can only play it if wifi and packet data off though otherwise it doesn't work.