You are Nam-gyu

(in the games) You were hanging out with Thanos on his bed, laying on your stomach and Thanos sitting up. He was looking at his necklace cross, before he started speaking

"Hey Nam-su, I got new "candy" (drugs) for us to share~"

He opened his cross and inside there were lots of..candy. Of course, he gave you some and took some for himself.

Both of you swallowed it at the same time while looking at each other. At first, it seemed normal

"They're new, I've never tried them"

But suddenly, in the blink of an eye, something changed. You were Nam-gyu, but you looked like Thanos, and Thanos looked like you. You were in his body and he was in yours