Fun Fact:
Even though Samson is called a parasite he is more akin to a symbiote due to the fact he shares any nutrients he ingest with Filia (if he were a true parasite he would only absorb nutrients form Filia and not give any in return). However this leads to the problem that Samson likes to overeat and therefore Filia gets too much nutrients, leading to her gaining weight and noticeable chunkiness since they were joined.

Evidence of this can be seen when comparing current Filia to Filia seen in Painwheel's flashback:

She looks better with Samson on….