Say whatever you guys want, if you were in his situation you'd have to reconsider this as well for a bit.
I think, in the end, he won't leave Tae for Reika. He might end up making the mistake of sleeping with her, but at the end he will remain with Tae. Reika seems like the kind of character that only exists for this romance tension anyway, so I expect her to die in a Gantz game when these internal love struggles are over.