  We observed the 2015 July-August long outburst of V1006 Cyg and established
this object to be an SU UMa-type dwarf nova in the period gap. Our observations
have confirmed that V1006 Cyg is the second established object showing three
types of outbursts (normal, long normal and superoutbursts) after TU Men. We
have succeeded in recording the growing stage of superhumps (stage A
superhumps) and obtained a mass ratio of 0.26-0.33, which is close to the
stability limit of tidal instability. This identification of stage A superhumps
demonstrated that superhumps indeed slowly grow in systems near the stability
limit, the idea first introduced by Kato et al. 2014, arXiv:1406.6428). The
superoutburst showed a temporary dip followed by a rebrightening. The moment of
the dip coincided with the stage transition of superhumps, and we suggest that
stage C superhumps is related to the start of the cooling wave in the accretion
disk. We interpret that the tidal instability was not strong enough to maintain
the disk in the hot state when the cooling wave started. We propose that the
properties commonly seen in the extreme ends of mass ratios (WZ Sge-type
objects and long-period systems) can be understood as a result of weak tidal
effect.
