You are looking at a long button up shirt from Comme des Garcons Homme Plus. This white button up is from the Spring/Summer 2016 Season and was designed by Rei Kawakubo. It has been worn twice and washed.
This shirt is tagged as an Extra Small: this shirt fits true to size, but since...
slate blue wool (83%)/silk (17%) blazer with a black panel. Neat details—the spiral paneling continues to the cuffs of the sleeves, whose (functional) buttons face in opposite directions; likewise the pockets are set on the slant.
Like new—even has the extra buttons and spare fabric.