Time Out says
It's the highlight of the year for Tokyo's hop heads: an afternoon of hardcore tasting, with over 100 varieties of craft beer on offer and the kinds of crowds you might expect on the Yamanote line during rush hour. Once you've paid the admission price for the Great Japan Beer Festival, you're free to drink all the brews you can stomach for the next three-and-a-half hours (though bear in mind that you'll be supping it from a 50ml tasting glass each time). Rare beers abound, with queues to match. Note that admission is limited to 1,500 people for each session, and the event often sells out, so you might want to pick up a ticket in advance.