For anyone looking to try this - while they sell pre-bottled mugicha [1], I highly recommend making your own from tea bags [2].
It's incredibly easy to make - just add cold water and let it sit in the fridge for a couple hours. It also tastes so much better (in my opinion), is much cheaper, and is more environmentally friendly.
A big 2L thermos filled with mugicha and ice is a great way to stay cool in the summer.
Even better to avoid the tea bags which are full of microplastics (though they will impart less when unheated)
It’s a well-known East Asian trope but I still reminisce about going to going to my grandmas house in summer and opening the fridge to drink some home made ice cold mugicha!