Bro

Bro
I think Okaya has a twisted obsession with Nagare, because even until so long he still kept a photo of them together in his phone.

It's reminding me of Dan from the Brutal manga, where...... SPOILER
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YOU'RE WARNED
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...where Dan orchastrated the bully of his crush, because he loves him. There's something wrong with Nagare (check the comments below by user named 'your nanny', they whipped out a good theory), and even more wrong with Okaya. As though two sides of the same coin that will forever never come face-to-face.

Okaya doesn't view himself as a god, I believe this could be a keypoint or a clue that may explain how he viewed Nagare. To me, it seemed as though Okaya was 'offerring sacrifices' to appease Nagare, albeit Nagare obviously not liking it. But somehow Nagare kept getting excited when he met someone that's in trouble, he wants to save them (it's not wrong wanting to save someone, but wtf Nagare why u blushing when you heard Ajiki could be a victim). Nagare wants to be a hero, and Okaya gives him multiple chances for that, even going as far as to see how much it'll take to break Nagare.

The word 'god' and 'demon' kept appearing in the same manga, one can't help but draw the similarity of Okaya behaving like a demon tempting for the fall of Nagare. I'm not entirely sure if Okaya views Nagare as a god / messiah / his Eve / Job (ya the faka whose kids got killed yet still loyal af to his 'god'/convictions), but he sure as hell is obssessed with this faka even after faka died.
And then you have Maria constructing an almost temple-like altar for her son Nagare.