Kappa restaurant is very good if you would like koryori traditional Japanese food (not sushi). You have to make a reservation because it has something like 7 seats total.
http://www.kapparestaurant.com
Benkyodo is the best place to get mochi.
If you want to try Japanese style pasta you can go to On the Bridge. It’s just a cafe - not a special place - but there aren’t many places in SF where you can get mentaiko spaghetti or natto spaghetti.
The Nijiya market on the corner is a pretty good grocery store and has items to go.
I usually go to Tanpopo for ramen in Japantown, but I’ve heard Waraku might be better. In general the best sushi places and ramen places in SF are not in Japantown. (For sushi that’s especially the case now that Ino sushi is closed.)
