MASTER OT J055845.55+391533.4: rapid decay of superhumps Superhumps in this object rapidly decayed (compared to ordinary SU UMa stars, but similar to AM CVn stars). The object may have already started fading rapidly and further continued observations are requested to know the nature of the (expected) second outburst. Observers: Tonny Vanmunster, Kiyota-san and Kubodera-san.