When Imperial Prince Munetaka, a son of Emperor Gosaga, became the sixth Seii Taishogun (literally, "great general who subdues the barbarians") of Kamakura bakufu (Japanese feudal government headed by a shogun) in 1252, Shigefusa moved to Kamakura together with the prince to be his attendant.
1252年（建長4年）、後嵯峨天皇の皇子宗尊親王が鎌倉幕府第6代征夷大将軍に就任するが、重房はその介添えとして共に鎌倉へ下向した。