Eviota sp.
Eviota is a Goby.
These are both Eviota sp. I just don’t know which.
Hairfin Pygmy Goby (Eviota prasites) アオイソハゼ
Shimadai’s dwarfgoby (Eviota shimadai) ハナグロイソハゼ
Shoulderspot Eviota (Eviota spilota)
Are the most likely candidates. The more I look the more uncertain I get.
They are Dwarfgobies and very small about 3 cm. Amami