(Yuushuu no bi wo kazaru; “To add a crowning touch”)
Carrying something through to a successful conclusion. Producing excellent results by seeing a task through with full effort until it’s complete, rather than doing enough work to finish and then coasting. Especially used to describe someone going above and beyond normal expectations to do their job or complete an assignment well.
This is a very simple sentence. Its verb is 飾る (kazaru), “to decorate,” “to adorn,” in sentence-final form. The particle を (wo) marks everything before that as the object of the verb. This noun phrase comprises the associative particle の (no) and the nouns 有終 (yuushuu), “perfection” (literally “having an end”) and 美 (bi), “beauty.”
A more literal (and poetic?) rendering might read, “To adorn with the beauty of an ending.”
Replacing 有終 with homophone 優秀 (“excellence”) is an error; the term 有終 is derived from a passage in the “Major Court Hymns” (大雅) section of the Zhou Dynasty text, the Classic of Poetry (詩経).
(“Morishita-shi wa hikaeme de itsumo jibun no koto wo mikkabouzu to ka roku de nashi to ka ittemasu ga, iza to nattara fugenjikkou de yuushuu no bi wo kazaru kata desu ne.”)
[“Mrs. Morishita is always very self-effacing, describing herself as someone who gives up quickly or isn’t very useful, but when push comes to shove she keeps her mouth shut and sees things through to the end.”]