This story is really well done and your analysis is on point.
What did u think of this new chapter? 704 is acting very unreaper like and he seems to have no fear of the king of hell's punishment for reapers with emotion and reasoning...the king does not want marines who think and feel for themselves, he wants obedient soldiers. Now I want to know how reapers are 'born'. Does 704 remember his time as a human as well as his real name? What is with the attraction yama shows for him? So many questions...
I have a lot of thoughts about your first question about reaper memories I won't spoil as it's based on the latest raw chapter but regarding your second question: I truly think Yama’s entire relationship with and attraction to 704 is a calculated act put on to appeal to and control Geumsun.
Yama doesn’t hesitate to get physically violent with 704 alone when 704 upsets him but repeatedly voices his concern for 704’s health in front of Geumsun. I think this is an entirely calculated act done to reassure Geumsun that 704 is in good hands so Geumsun can stop worrying about 704 and worry instead about Hwan.
Yama told Geumsun to send 704 to him so Yama could keep him safe all the while counting on 704 being able to escape.
I would not be surprised if Yama made some deal with Geumsun to release 704 if Hwan was killed and any possessive mentions of 704 is reminding Geumsun of the work to be done. When Geumsun calls Yama to pick up 704 he says “Keep him safe. Until I go get him again.” almost like it’s agreed that is what will happen if Geumsun succeeds. Yama makes no mention of 704 being “his reaper” here nor does he deny Geumsun of taking 704 back. Yama simply says “…fine. Good luck”.
I think if Yama had real genuine interest in 704 he would say no or be more difficult and remind Geumsun again who 704 belongs to. The easy agreement makes me feel like that is exactly what Yama wants. 704 is simply Yama’s possession to make Geumsun fall in line.
Ah, a tool.
Interesting point about Yama using Geumsun (king of Hell we're talking about here)! It seems both Geumsun and San are triggering 704's feelings now that he was able to put the pieces together. I'm really curious about 704 past. I think we all agree that 704 is actually the human Geumsun knew and not just someone that resembles him. And I'm pretty sure Yama did this on purpose, as you said, as a way to control him.
So, I was just wondering about the author's note on chapter 31.5, regarding how the protagonits share the same keyword. I assume this keyword is Memory, since we have San and 704 forgetting their previous memories (San on purpose), while Geumsun and Eunjae have difficult memories that they have to live with. Geumsun mentions how humans are blessed for being able to forget memories, something Eunjae did to protect himself (similar to San). He also mentions how Hwan is a being that compels humans to recall memories they want to forget (poor Eunjae!). Geumsun is the only one not blessed with this "gift of oblivion", something that clearly makes him feel bad. I think is really cool how Hwan's abilities relate to the story :)