I hadn't been to a true happy hour in years, but the other day I stumbled into the one at O Izakaya. Beers, well sake and well drinks were each $3, which seemed like a pretty good deal (I drank Sapporo). What was a great turn on, though, was the food, priced on a special happy-hour $5 list. We sampled the seaweed salad, ultra-fresh hamachi and the tempura/beer-battered onion rings and loved all of it.
Izakayas in Japan are drinking establishments with more-sophisticated food than the snacks you'd find at just a regular bar--sort of a Japanese gastropub, I guess you'd say. O Izakaya certainly qualifies as this, even if the atmosphere seems a bit generic (besides the wonderful window shades painted with comic-book style renderings of Japanese baseball stars). Put it on your list of places to go in Japantown, especially at happy hour.