On the brewing instructions that they send out, Den mentions that his grandfather liked brewing hashiri shincha with boiling water, and that he likes it as well. The instructions go on to recommend playing with the parameters too, to see how it affects the flavor so you can find what you like best. The only rule of thumb is higher water temp = shorter brewing time, lower water temp = longer brewing time.
So I just had to experiment and try it with boiling water.
It was STILL excellent. The bitterness (or young/fresh flavor) was more pronounced, but not at all overpowering. With a low quality green tea, boiling water can make it undrinkable, but not with hashiri shincha. While it wasn’t my favorite brewing thus far, it was still delicious and I would definitely do it again. All of the previous flavors I’ve talked about were present and came through after the initial rush of young bitterness and then intense sweetness. Even an amateur like me can tell the difference; this is good tea and I recommend it to anyone who likes Japanese green tea!