A friend of mine passed on this address which is accepting clothes donations.
Miyagi ken, Watarigun
Watari cho Aza kyuukan 62-1
Sato kinen Taiikukan
Their number is 0223-34-0505
They're looking for high quality spring and summer clothes with little or no signs of wear. They don't need winter clothes because they can't store them, or underwear as the shops there are starting to reopen.