Oops, it doesn't look like 'koichi day' is a national day..

Other days

tulip

Tulip Day
ride the wind

Ride The Wind Day
bubble bath

Bubble Bath Day
ponytail

Ponytail Day
kale

Kale Day
aloxolt

Aloxolt Day
girl friend

Girl Friend Day
self appreciation

Self Appreciation Day
youth

Youth Day
hoodie

Hoodie Day