Re-infusion is an integral part of the Japanese green tea experience. Contrary to some habits, it is not a matter of using "leftovers" a second time, but rather of several successive infusions, each with its own character.
After the first infusion, the leaves have already begun to open, but they still retain much of their aroma. This is why it is recommended not to leave them in the water, in order to control each extraction and avoid unnecessary bitterness.
Sencha can generally be infused three to four times, with its flavor profile evolving with each infusion. Gyokuro, denser and richer, can be infused even further, up to five times. It tends to offer a very concentrated first cup, then gradually softens, becoming lighter and more delicate with each subsequent infusion.
To complement this process, it is advisable to slightly increase the water temperature with each infusion. This allows for the gradual and balanced extraction of what remains in the leaf.
The only limitation is time. Leaves left exposed to the air for too long quickly lose their quality. Ideally, infusions should be carried out within a relatively short period to fully benefit from their potential.