They have a little special section of items for sale via jewels to raise money.
The article about it can be found on the front page, but here's a direct link
The beneficiary is the Japan Red Cross.
Purchasing an item of 50 jewels = donation of 50yen to the Red Cross.
Pupe will donate the same amount with each donation. Meaning ultimately Pupe will give 100yen for an item costing 50 jewels.
Above specifics added courtesy of elze_art
In a separate announcement, they said they will temporarily stop new releases on their site because of the tragedy.
Please continue giving Japan your support in any way you can!