“White day” is the day when men send presents for women to express their usual appreciation. This event seems to be unfamiliar in Europe or USA and somehow familiar to east asia.
In Japan, men present some confections or flowers to women as a reciprocal gift for valentine day’s present.
Fortunately I found nice confections on the local tea festival in Makinohara, I could present baked cakes containing green tea powder and Yuzu citrus with nice flowers.