I have never made a foreign trip solely for birding, but try to find time for some birding, along with the standard itinerary of museums, dining, photography, etc., on every overseas trip. It helps to book a hotel near a birding hotspot, and that is what I did for my first trip to Tokyo. A little preliminary research revealed Hibiya Park in Central Tokyo, near the Imperial Gardens and Palace, as a good urban destination, with the outstanding Imperial Hotel just across the street. This large park contains two ponds, a fountain, and various urban habitats that allow good urban birding. This gave me some time for early morning birding (sunrise is very early here in April) while my wife slept in, meeting later for breakfast.
Several early outings in the park revealed 13 birds, including several lifers. Even the “common” birds are exciting sitings in your first trip to any location. These were Great Egret, Rock Pigeon, Large-billed Crow, Barn Swallow, Brown-eared Bulbul, Oriental Turtle Dove, Oriental Green Finch, Azure-winged Magpie, Japanese Tit, White-cheeked Starling, Dusky Thrush, Eurasian Tree Sparrow, and Brambling, with some photos of these below.