Ukraine U23 have the advantage in terms of age compared to the side from Japan formed from players of max 19 years age. Ukraine U23 smashed Italy U21 with 4-0, won 2-0 with Panama U23 and 3-0 with Indonesia U20. Japan U19 won 4-1 against Indonesia U20, but that is really a weak opponent, they were 2-0, 3-1 and 4-2 behind with Italy U21 while losing 4-3 in the end.
Japan has a weak defense, Ukraine is strong in defense and won all their games to nil and by min 2 goals difference, actually they won 2-0, 3-0 and 4-0 so far. So I back right here Ukraine U23 to secure top place this group stage and to be playing in the final of this tournament for sure, that being said, Ukraine U23 compared to Japan U19 is too much for the Asian side which can not defend well at all, and I take Ukraine U23 with -1.5 AH.