A Crucial Item

Ahh... the blossom of gods. This item is crucial to continue your journey. By what we know, its obtainable after fighting 3 guys. what those 3 guys are, we don't know. Although, the item isnt released yet, we do know a bit of info, due to what Michael says about it. he says "So, the blossom of gods. sounds like a familiar thingy i was researching while in the lab... didn't it say something about the fifteen.". Yeah. Thats all we know... but anyway. It seems to be connected with fifteen... what does the fifteen mean not number-wise.