Might as well chime in being that I live here too. As stated by the others I'm not sure what you have done so I might duplicate something. I'd recommend you letting us know what you've done so far in a few points. But here goes.
@aquamarine He also lives here so I think his list is pretty good for Tokyo. Things that give you a taste of mostly the new and exciting. Which is mostly what Tokyo is famous for. While there are a few less popular things and places to go I'm afraid that they'd bore you.
@isityours I get the feeling that he's visited with some poor personal xperiences and or has a few misguided conceptions. Roppongi day or night is an ok place to be with or without a female companion. The art museum in the Mori Tower always has some wonderful exhibits.
I do have to agree with him on Fukushima, there honestly isn't much to see or do as it's still in the rebuilding process. Of course it's not the entire prefecture and there's still a bit to do like seeing the Aizu Festival (会津まつり) in late September.
Both suggest a bath and I do too but I have to imagine that you did that already. It's true that they will shoo you away if they notice any ink on you after getting naked and even after paying. But they will most likely re-pay you. I honestly enjoy Sentou's just as much as Onsen. Yes there is a technical difference but to me a bath is a bath.
The eating is wide and varied. I'm not sure what you're dietary habits are so I can't recommend anything with confidence.
I have to imagine that aqua's recommendation of raw liver was for shock value. Of course there are those of us that have strong mental barriers to certain foods and can't lower them to try new things. But I ave been able to shed most while living here for so long. Raw liver while not a favorite of mine is very good when done well. Which usually is the case. I wouldn't let isityours horror story of wasting away a trip due to poorly prepared food scare you away from trying it. The water anywhere is fine and the food the same.
Horse, dolphin, turtle, shark, & whale… the list of animals that many if not all westerners consider
NO NO is long and varied. Obviously isityours is a bit against consuming some if not all. Humans have always eaten everything. This and all your trips should be used as a tool to further experience different cultures and lifestyles. You can make the choice yourself but if you've got questions about them feel free to ask.
Finally I would backup isityours recommendation for Kobe or Kyoto. Not as a replacement for Osaka but in companion. From Tokyo to Osaka then back to Fukushima will add time and money to the travel. Kobe, Kyoto & Osaka are all Kansai so relatively close saving hours and Yen in going from place to place. Of the three I'd recommend Osaka and Kyoto.
The amount of things to do and see in Kyoto is incredible. There are tons of books written on it alone. I'd have to write a whole other reply just for that. But let's her what you have to say so far.
