  Continuing the project described by Kato et al. (2009a, arXiv:0905.1757), we
collected times of superhump maxima for SU UMa-type dwarf novae mainly observed
during the 2012-2013 season. We found three objects (V444 Peg, CSS J203937 and
MASTER J212624) having strongly positive period derivatives despite the long
orbital period (Porb). By using the period of growing stage (stage A)
superhumps, we obtained mass ratios for six objects. We characterized nine new
WZ Sge-type dwarf novae. We made a pilot survey of the decline rate of slowly
fading part of SU UMa-type and WZ Sge-type outbursts. The decline time scale
was found to generally follow the expected Porb^(1/4) dependence and WZ
Sge-type outbursts also generally follow this trend. There are some objects
which show slower decline rates, and we consider these objects good candidates
for period bouncers. We also studied unusual behavior in some objects,
including BK Lyn which made a transition from an ER UMa-type state to the
novalike (standstill) state in 2013 and unusually frequent occurrence of
superoutbursts in NY Ser and CR Boo. We applied least absolute shrinkage and
selection operator (Lasso) power spectral analysis, which has been proven to be
very effective in analyzing the Kepler data, to ground-based photometry of BK
Lyn and detected the dramatic disappearance of the signal of negative
superhumps in 2013. We suggested that the mass-transfer rates did not vary
strongly between the ER UMa-type state and novalike state in BK Lyn, and this
transition was less likely caused by a systematic variation of the
mass-transfer rate.
