It's Chinese. 南， Pronunced as "nan", means "south". Could be Japanese Kanji since it's essentially just slightly modified Chinese. Probably some note left by the developers but forgot to remove it during modeling.
I saw a symbol like this but much more simple in SH3. I didn't take a shot, since was my first time playing this game, hope to see it again. These game has a lot of cool things like this - make the experience more rich.