  We observed the 2016 outburst of OT J002656.6+284933
(CSS101212:002657+284933) and found that it has the longest recorded
[0.13225(1) d in average] superhumps among SU UMa-type dwarf novae. The object
is the third known SU UMa-type dwarf nova above the period gap. The outburst,
however, was unlike ordinary long-period SU UMa-type dwarf novae in that it
showed two post-outburst rebrightenings. It showed superhump evolution similar
to short-period SU UMa-type dwarf novae. We could constrain the mass ratio to
less than 0.15 (most likely between 0.10 and 0.15) by using superhump periods
in the early and post-superoutburst stages. These results suggest the
possibility that OT J002656.6+284933 has an anomalously undermassive secondary
and it should have passed a different evolutionary track from the standard one.
