Ōshuku

Prunus Mume
Japanese Apricot
Ume

Ōshuku
鶯宿（おうしゅく)
'Ōshuku' is typically grown for fruit,  but will produce enjoyable flowers, and can also be used for bonsai.  The history of this cultivar can be traced back to the Nanboku-chō period (1336-1392).  Its flesh is hard, and it is known for its use in umeshu!

Primary uses
Umeshu and ume juice.  Umeboshi will be particularly firm