Good episode. Glad they're back to actually doing their job! So wee now know about both Black Market Retrievers and the somewhat confusing term Android Children.
Wee now know that Michiru is an android child, having been brought up by a Giftia father (at least?) who 'expired' before he was retrieved and became a wanderer. Michiru seems to be okay at present (no evident burden distressing her) and there was no implication that anything else happened after her foster parent of sorts became a wanderer but that might be something that's brought up again later.
Isla wasn't so much of a focal point this time but the main problem addressed is relevant to her situation - the problem of memories and whether they should have value to androids. Given how advanced Giftia's are, if they are capable of sustaining memories and having emotions they shouldn't hold a different value to their memories than humans do. Sure they are made as products, to fulfil roles, but they are clearly allowed and are encouraged to have relationships with humans and that could only work if feelings are mutual between android and human. Isla could end up regretting being so insular and wasting the little time she has feeling that emotional attachment and making memories are ultimately meaningless things, unfortunately. This 'expiration'... 'what's the point of living if wee die' idea is not new to us humans, though... maybe she needs to be reminded of that and that she has no reason to think she and other Giftia are different in that respect. One must try to live life to the fullest.
Could it be that Kazuki wanted to break off her partnership with Isla because she wanted to create distance so losing her will be less painful? A sad thought but it's a possibility, and it seems Isla might have figured that much out given her flashback.
Now wee can expect Episode 5 to be about Black Market Retrievers - what's in it for them? Spare parts? :/
Edit: Oh yeah, well done Isla... it's a start! xD