Japanese white pine; Pinus parviflora
A five-needle pine native to Japan, often used in bonsai and gardens. The name 姫小松 literally means 'princess small pine'.
I planted a Japanese white pine in the garden.
small pine used in ne-no-hi-no-asobi
Specifically a small pine pulled from the ground during the ancient courtly game 子の日の遊び (ne-no-hi-no-asobi), a New Year's custom of uprooting small pines for good luck. Rare historical/cultural term.
See also: 子の日の松
During ne-no-hi-no-asobi, people pulled up small pines and wished for longevity.
Compound of 姫 (hime, 'princess; small and lovely') + 小松 (komatsu, 'small pine'). The name reflects the tree's delicate appearance.