nobuo sekine (関根伸夫, sekine nobuo; september 19, 1942 – may 13, 2019), was a japanese sculptor. he was one of the key members of mono-ha, a group of artists who became known in the late 1960s and 1970s. he was born in saitama, japan. in october 1968, he created his best known work "phase: mother earth" in kobe’s suma rikyu park for the "first open air contemporary sculpture exhibition" (第一回野外彫刻展).