Filling the halls of a wooden building from 1885 (actually the old Hakodate Quarantine Office) is this magical teahouse overlooking the water. It's lit only by natural light so closes after the sun sets. In the meantime, you can while away the afternoon refilling your tiny pot of single-origin green tea, nibbling on the wagashi (Japanese sweets) and pickles that accompany it.
The teahouse is a short walk beyond the Foreigners' Cemetery.