Ootoya is an excellent all-around Japanese restaurant that serves rice donburi (Chicken or fish on rice), soba and udon.
There is an English menu as well as pictures. There are vegetarian dishes available.
It is across the bus rotary from the SOUTH exit of Otsuka Station. It is on the 2nd floor of a building.
Google Maps: http://goo.gl/maps/MMb4d
Abura Soba! 油そば
I don't even know how to explain this. It's literally translated as "oil noodles". It's a kind of soup-less ramen. Just try it! There is no English menu, but there are pictures. When in doubt, simply order "Abura Soba!" (pronounced as AH-BU-RA SOH-BAH)
Google Maps: http://goo.gl/maps/1IPoR
Udon noodles うどん
Enjoy Japanese udon, made fresh daily in the restaurant. There is not an English menu, but you can point at the pictures on the wall. I recommend the udon which you dip into the soup and eat. :)
Google Maps: http://goo.gl/maps/SSHor
Sit down and make your own okonomiyaki with the grill in front of you! There is no English menu, but you may ask for a recommendation or "Osusume" in Japanese.
Google Maps: http://goo.gl/maps/2sdca
Gyuudon (beef/pork and rice) 牛丼
You'll see Yoshinoya with it's orange sign. Here you can order beef over rice or pork over rice etc. It is foreigner friendly as they have an English menu. It is very affordable and considered as an original Japanese 'fast food'.
Google Maps: http://goo.gl/maps/ETUrB
Sit down on the open counter and order "Ramen!" This shop specializes in Tonkotsu ramen, which is pork broth noodles. It's fast and affordable!
Google Maps: http://goo.gl/maps/gW5hJ
Kaiten Zushi 回転寿司 (Conveyer belt sushi)
It's sushi that goes round and round on a conveyor belt! Take what you want to eat. If it is not on the conveyor belt, then you can order it directly from the old man behind the counter. English menu is available!
Google Maps: http://goo.gl/maps/8BGJ8
Izakaya 居酒屋 (Place for drinks and Japanese tapas)
Izakaya is a general term for a tavern or a place to eat and drink with friends. It's not a place to socialize with strangers, but a good place to sit down and chat with friends.
If you're looking for Japanese tapas style food and alcoholic drinks, this is an interesting place to go. You can order with a touch pad monitor which has the menu in English and Chinese languages.
Google Maps: http://goo.gl/maps/IJnUy
(Map does not work well on smartphones)