Pustulose Nudibranch (Phyllidiella pustulosa) コイボウミウシ
I believe these are all Pustulose Nudibranchs (Phyllidiella pustulosa). This one is on the ceiling of a cave with a flash. Amami 2023
This one seems to be covered with mucus. Amami 2024
A close up of the front of a Pustulose Nudibranch. Amami 2024
This one is a bit more active and looks a bit different. There seems to be a bit of variation in Phyllidiella pustulosa. There are also other Phllidiella sp. that look similar too. Amami 2023