Yeah but I have already thrown 3 Rainbow Spirits at that last skill up with no luck so I am being stubborn now. I hate wasting rainbow spirits on event units when it is possible to get skill ups easier than those that aren't events units like my black Sybilla.
I know a 1/4 beats 1/20 chance of skill up when using rainbow spirit, still I will see how my luck fairs though I don't have high hopes for the 5% chance.