Blue Demoiselle (Chrysiptera cyanea) ルリスズメダイ – size 8cm
This male Blue Demoiselle is blue with a dark line going from above the mouth through the eyes and fading as it goes back. Some have orange on the back of the tail and sometimes around the mouth. I have not seen that around here. They can get up to 8 cm. Amami 2023
Another male Blue Demoiselle. They are larger than the females and have a more rounded tail. Amami 2025