When in the summer specifically?
Since you're interested in eating I'll suggest what I do best, suggest places to eat.
Please note that this is Japan and for me to walk out of any restaurant satisfied, it's at least 60 bucks for Haru and I at any given restaurant.
Gyukaku- AMAAAAAAAZING yakiniku. Even if you've been to one of their American stores you've gotta visit. I suggest ANY of the skirt steak selections (assorted kinds of harami) and their sesame oil cabbage.
Onyasai- AMAAAAAAAZING shabushabu. If you order the all you can eat (tabehoudai) you'll be in meat heaven. Ordering WILL be a hassle without a Japanese speaker I guarantee you this. However, the rewards are worth the 5 or so minutes of pantomime.
DomaDoma- AMAAAAAZING Japanese pub food. My personal favorite menu item, Kishimen Carbonara. I could eat 5 plates of it if it wouldn't give me early heart disease.
Kentucky Fried Chicken- Teriyaki Twister. Unless you like seaweed for some reason ask for it with 'nori nashi de kudasai'.
Burger King (Shibuya)- They may not have anything special on the menu but it's worth a look. Their jalapeno Whopper was incredible and gave me the most painful shits of my life. Totally worth it.
McDonald's- Gotta eat the Teriyaki Burger. Every gaijin does at least once.
Bikkuri Donkey- Maybe a little bit tougher to find but it has the cheapest and biggest German-style meat loaf (hambaagu) of any chain I know.
Hungry Tiger- More difficult to find and although they aren't as big as Bikkuri Donkey's loafs, they're DELICIOUS.
Skylark/Gusto/Denny's/Jonathan's/Big Boy- It's worth it to try a Japanese family restaurant. I promise you'll never see some of the stuff on the menu at a Denny's in the States.
This is useless since I've forgotten the name but there's a gyoza restaurant in Shibuya RIGHT near 109 that's OUT OF THIS WORLD. I never thought they could make a full-fledged restaurant based on gyoza but they're deliiiicious.
Any bakery (bread store). No matter where you go you're bound to find something delicious at a bread store. You'll find things that you never IMAGINED going together and they're divine. Don't be afraid of tuna and corn.
Circle K or Sunkus convenient stores- They have BAR NONE the most delicious tuna onigiri. You can get them from either place because they're basically the same thing.
Lawson- Three words 'karaage-kun reddo'
Family Mart- Try their dessert section, they've got some sweet stuff but it used to be better. They've gone more French with desserts and they lost the bold taste they used to have.
Sushi, wait for Kyoto before you even attempt sushi.