Obana is certainly not the most illustrious of Tokyo's unagi restaurants. How could it be when most of the flash money lies west of the Ginza, not up in blue-collar Arakawa-ku? But there are plenty of people, especially those of humbler birth, who will go to the grave swearing by the name of their ancestors that nowhere in the city prepares broiled eel better than this.
As with all the best things in life, a meal at Obana requires time -- plus a certain sense of adventure. Unless you live to the northeast of Ueno, you will first have to budget in the half hour it takes by train (or subway) out to Minami-Senju, where the JR station is so quaint you could be out in rural Ibaraki-ken.
Then, once you get there, you should be prepared to take your place in line. Obana is surprisingly overlooked by the media but not by the local populace, which descends in droves by car, bike or foot, especially at weekends and on holidays. Those in the know bring books to occupy themselves; others just huddle in the shade, fanning themselves and admiring the restaurant's handsome exterior, recently rebuilt but along traditional lines, complete with gateway, shrine and pebbled courtyard.