Ogura pretty much explains the Kei's situation tho, since he manifested at birth so his IBM intensity is dense and since he has been letting it out unconsciously for so long it practically became a body of its own and can last longer than any of the other Ajins. As for Tosaki (i forgot the chapter number) but before we last see him after his press conference, he was heavily injured in the stomach by Sokabe and then he eventually bled out at last moment on that bench
I don't know how anyone could have any sympathy for Tosaki. I think Sato was a true villain for killing innocents but I fully support him annihilating everyone who knowingly involved themselves in the experiments. No matter what was up with his fiance, he still did unforgivable things and never regretted them. There are ethics even in scientific research and he destroyed all of them. I don't even think the girl under Tosaki was forgiveable either and it's messed up that the author hinted at something between her and 002 at the end. It is disgusting. Tosaki deserved that ending and I am glad his fiance never woke up to see the monster he had become.

I have so many questions and thoughts..
But what happened with tosaki ? His story was depressing he lost everything . I feel bad that he got the sad ending out of everyone
And I wish they talked more about Kei's IBM manifesting at such a young age and how it let's him summon a bunch