Benthic combjelly on Luzon seastar (Coeloplana astericola)
Weird, can't find any info about this highly conspicious flatworm, that I saw on a couple of seastars in Tulamben. It seem to be spawning or defending itself. It also has 4 holes/bubbles in the centre. This is an isolated animal. I saw a seastar with more than 10 of these on it. Looks parasitic to me.
* Update. Solved.
Seastar might be Linckia guildingi