Ajisai is the Japanese for hydrangea flower which blooms during the rainy season (May - June)
This is a kohakutō which is made by mixing kanten (seaweed jelly) with sugar, cut into the shape of hydrangea petals, and then dried for a few days.
Best-before date: 2 weeks
Availability: May - June, all stores.
Kanten (seaweed jelly)
Kanbaiko (mochi flour)