“Spike winter hazel” トサミズキ（土佐水木). (These are easily mistaken for “unusual” robai or wintersweet.) I did a double-check at the nursery and this plant is called tosa mizuki which is Corylopsis spicata Siebold or Winterhazel. Winterhazel is also fragrant being related to the witchhazel plant. This is one of two native winterhazel or Corylopsis. The other one is Corylopsis pauciflora which is good for bonsai-ing.
Info from the Garden Club:
A Soft-yellow Fragrant Shrub to Announce the Arrival of Spring
Tired of harsh yellow flowers like forsythia and King Alfred daffodils in the early spring? Not as common is another shrub that not only blooms at the same time as the forsythia, but has a profusion of pastel yellow, fragrant blooms that will brighten up your garden as winter turns to spring – Corylopsis spicata or Winterhazel.
Corylopsis spicata is by far the most handsome of all the Corylopsis and the earliest to bloom. Beginning in March, pendulous 2 inch chains of lemon-yellow blooms appear on the bare branches. They are somewhat reminiscent of wisteria blooms in shape, but on a much smaller scale. The fragrance is spicy and sweet, similar to that of witchhazel to which winterhazel is closely related. New foliage will soon appear, unfurling a dark purple and maturing to a deep blue-green with lightly felted undersides. Corylopsis spicata will slowly develop into an attractive, broad mass of horizontal branches, reaching 6 to 8 feet tall and wide. It is a prefect accent in front of a dark backdrop, such as a dark wall or evergreens, and is ideal for border or mass plantings. Corylopsis spicata works well when planted as a mid border planting dressed down with Rhododendron PJM, Azalea poukahanese or Crocus tomasinianus in the foreground – all of which bloom at the same time as the winterhazel.
More info on the different types of Corylopsis at this link.
Corylopsis is a genus of nearly 30 species of shrubs in the witch hazel family, Hamamelidaceae, native to eastern Asia with the majority of species endemic in China but with some also in Japan, Korea and the Himalayas. They grow to 2-6 m tall, and often with a crown wider than tall. The leaves are ovate with an acute apex and a serrated margin, 4-20 cm long and 3-15 cm broad. The flowers are produced in late winter in pendulous racemes 3-9 cm long with 5-30 flowers; each flower has five pale yellow petals, 4-9 mm long. The fruit is a dry capsule 10-12 mm long, containing two glossy black seeds.