AMAZING welcome and SUPERB LOCATION!!! ometosando and harajuku are on walking distance. You can get the circle line yamanote that goes basically all around tokyo. And have the ginza line that stops at all the spots you need!
No need to get a sim card if you stay in tokyo. Hiro has a pocket wifi that worked amazing, you can also grab it with u if u do daytrips. If staying in Tokyo they have wifi almost everywhere in tokyo for free.