  The JSNS$^2$ (J-PARC E56) experiment aims to search for a sterile neutrino at
the J-PARC Materials and Life Sciences Experimental Facility (MLF). After the
submission of a proposal to the J-PARC PAC, Stage-1 approval was granted to the
JSNS$^2$ experiment on April 2015.This approval followed a series of background
measurements which were performed in 2014.
  Recently, funding (the grant-in-aid for scientific research (S)) in Japan for
building one 25~ton fiducial volume detector module was approved for the
experiment. Therefore, we aim to start the experiment with one detector in
JFY2018-2019. We are now working to produce precise cost estimates and schedule
for construction, noting that most of the detector components can be produced
within one year from the date of order. This will be reported at the next PAC
meeting.
  In parallel to the detector construction schedule, JSNS$^2$ will submit a
Technical Design report (TDR) to obtain the Stage-2 approval from the J-PARC
PAC.The recent progress of the R$\&$D efforts towards this TDR are shown in
this report. In particular, the R$\&$D status of the liquid scintillator,
cosmic ray veto system, and software are shown.
  We have performed a test-experiment using 1.6~L of liquid scintillator at the
3rd floor of the MLF building in order to determine the identities of
non-neutrino background particles coming to this detector location during the
proton bunch. This is the so-called "MLF 2015AU0001" experiment. We briefly
show preliminary results from this test-experiment.
