Various subway passes with different coverage are described on this site
http://www.japan-guide.com/e/e2017.html
On a typical day, I don't travel enough to make any of the day passes worthwhile. YMMV. I don't even bother thinking about them - I just use a prepaid IC card (SUICA) which gives me flexibility to use virtually all modes of public transit by paying the fare each time.
OP appears to have convinced himself that Tokyo is going to be a huge challenge, but as many point out, the multilingual signage and wayfinding systems are abundant. While they don't work in exactly the same way as the ones in your home country, it won't take you long to work out.