Btw u can mark the comment as spoiler so it won't be as visible
My theory? I think the one whose face we were about to see on the plane was Nagai’s dad that randomly disappeared. Maybe he found out his kid was an Ajin from a young age (remember, it was mentioned he was a doctor and Nagai was following in his footsteps) and somehow got into the force after training. That’s why he never showed up again because he was undercover and had to be ‘missing’ or ‘dead’ for the safety of his family. Would also explain why he’s practically on the same wavelength as his son when it came to the mission and that last scene. The only plot hole would be when they first touch down and make contact with him on the airstrip, but he might just not recognize his son/be trying to neutralize a threat to the mission until he got confirmation that Nagai was a ‘good guy’. Idk, just my fan theory ╮(￣▽￣)╭
Spoiler warning : why the hellll did they freeze Sato instead of containing him and letting him die of old age?! If they wanted Demi humans to experiment on (not that I like that idea) why not use the other criminals ? Also any theories about who the special task force people were ？I’m leaning towards Aijin in a different country, perhaps the contained American ones - using their shadows as remotely controlled soldiers. Which is why they were able to see the other shadows / their bullets were able to affect the shadows … probably used parts of the shadow body as bullets.