sharingun can only see limited chakra flow it cant pin point were his heart would be because sasori's chakra would flow throw his puppets the same way he wouldnt be able to tell were sasori iskakashi team easy.
sasori will die in 10 second ,sharingan detect the sasori's heart position+ kamui his heart the end. (1/3 of kakashi chakra gone )
darui kill kakuzu 3 time with Ranton
kakashi let kakuzu trap him , like in there first fight ,but this time he use again kamui on him and kill all his last heart or jsut use a raiton bunshin for freeze kakuzu and raikiri is enough.
What?sharingun can only see limited chakra flow it cant pin point were his heart would be because sasori's chakra would flow throw his puppets the same way he wouldnt be able to tell were sasori is