Porn

Tokyoites are so starved for space, using a love hotel, even if you're a 'normal' couple, is considered reasonably standard practice. You can rent a room for, say, two hours, typically decked out in some wild setting, and then continue about your business.
That said, of course the densest clusters of love hotels are in areas where the more conventional red light district services are also on offer. There, you won't have a hard time finding your way around, if you're Japanese. 18+ only information shops give you the lowdown on what service to get where, what to pay for it and which girls to ask for. All in high tech fashion, with rows of flat panel screens giving you access to all the services available in the neighborhood.

Porn shops are not exactly everywhere, but easy to find. DVD shops have a stack of shopping baskets at the door. You pick a basket, load a stack of DVDs from the shelves into it and retreat to a private cubicle.
And everything your heart might fancy is on offer. Including stuff that would put tub girl to shame.
If you have a slightly weak heart, you might not want to click on that previous link. Unless you've got safesearch turned on in Google.

If a creepy mind ever thought of it, it's for sale in Japan's porn shops. Hello Kitty vibrators? Check! Vibrating underwear (for girls)? Check. Vending machines selling used undies? Check (though I haven't found them yet).
And in Japan, they take fleshlights (again, you might not want to click on that link) to a whole new level. And they're cheap! The cheapest ones coming in at only some 3 euros! Hmmm… Maybe I should get a few as gifts…

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In the DVD stores, small screens continuously pump out Japanese porn. With the naughty bits censored. It made me wonder whether, if you buy or rent any of the DVDs, the naughty bits are also obscured.

Sights

The Shinjuku area is home to the Tokyo Metropolitan Government offices, where you can go up to the 45th floor, for free, and enjoy the scenery.
It's not the only skyscraper in the area you can go up in, the Shinjuku Sumitomo Building being another example.
One that's not free, the Sompo Japan Museum of Art, on the 42nd floor of the Sompo building, has the added attraction of van Gogh's Sunflowers which was acquired in the 1980s for 5 billion yen.

Tokyo opera city is considered to be one of the world's most acoustically perfect concert halls. In the same building, there are also two art galleries. While I was there, one ran an interestingly sounding show "Trace Elements", with the subtitle "spirit and memory in Japanese and Australian photomedia", which I thought was disappointing. The other gallery had a more lowkey but seemingly more interesting show on ASADA Hiroshi. However, I found the combined ticket price too much to justify a visit.