MASTER OT J055845.55+391533.4 superoutburst ZTF light curves of past superoutbursts have complex profiles. May not be an ordinary SU UMa star. YYYYMMDD(UT) mag observer 20210828.8465 <142c (Yutaka Maeda) 20210829.8457 <146c (Yutaka Maeda) 20210830.8308 <162c (Yutaka Maeda) 20210831.8157 <156c (Yutaka Maeda) 20210909.7884 146:cG (Yutaka Maeda) 20210911.1820 14.20cG (Masao Funada) 20210918.7888 <162c (Yutaka Maeda) 20210919.8442 <159c (Yutaka Maeda) 20210922.7850 <152c (Yutaka Maeda) 20210923.7868 153c (Yutaka Maeda) 20210924.7913 153:c (Yutaka Maeda) 20210926.069 15.14C (Gary Poyner) 20210926.0696 15.13C (Masao Funada) 20210927.7853 151cG (Yutaka Maeda)