well the point of IPA is that a symbol matches up to an internationally-agreed sound and /o/ is the close-mid back rounded vowel
however, what’s not listed is that it seems the elongation of a vowel in Japanese is suprasegmented - so the “doo” sound is closer to how you’d say the o’s in the (nonsense) phrase “do oozing” - a very subtle distinction from just “doo”
it’s possible that Japanese speakers could endolabiallize differently, or that they form the vowel closer to open-back than close-back like /《o̞》 / but I’m not an expert
well the point of IPA is that a symbol matches up to an internationally-agreed sound and /o/ is the close-mid back rounded vowel
however, what’s not listed is that it seems the elongation of a vowel in Japanese is suprasegmented - so the “doo” sound is closer to how you’d say the o’s in the (nonsense) phrase “do oozing” - a very subtle distinction from just “doo”
it’s possible that Japanese speakers could endolabiallize differently, or that they form the vowel closer to open-back than close-back like /《o̞》 / but I’m not an expert