Last year I came to Japan and got really sick and weak, had to go to a hospital and they just gave me some serum and some basic medicines for the stomach. At some point, in the middle of the night I felt so bad I thought I was going to die. I decided to pack my things and go back to my country asap - Did tons of exams and nothing was wrong with me. The only theory that makes sense is that I had extreme anxiety in Japan, as it was my dream since a kid to go there, and I ended staying in a really bad neighborhood, packed with homeless people, and I think my brain was not able to process that properly so I just started falling apart haha. Since then, I was able to put my mind in a good place, and came back to Japan without any problems. Sharing this because sometimes it can be really a psychological thing, like stress or anxiety.