Riki Watanabe
http://metrocs.jp/en/
'The Carton Furniture Series was originally designed in 1965 by Riki Watanabe and has been reproduced by Metropolitan Gallery in Tokyo. The Kids’ Set is made completely out of folded cardboard with no adhesives, nails, or screws. The stools are strong enough for the weight of most adults and all pieces are recyclable.'—via designmilk.