[bloak]

Lots of the world's languages have exactly five vowels corresponding to [a], [e], [i], [o], [u], but Japanese is a bit unusual in that the Japanese [u] is unrounded, so it can be more precisely (narrowly) transcribed as [ɯ]. Spanish has a more "typical" set of five vowels. You would presumably be understood all right if you used Spanish vowels in Japanese but you wouldn't sound like a native, so pronouncing [ɯ] correctly usually wouldn't be one's first priority in learning Japanese. In Russian and Turkish, on the other hand, you would have to make a distinction between [u] and [ɯ]. (I'm not an authority on any of this; I just dabble in phonetics.)