Starting from LHside kamai...
Shufflestep: Slide left foot forward whilst punching LH mae-ken-tzuki and guarding head with RH. Quickly draw right foot forward to regain kamai position and twist hips counterclockwise whilst punching RH gyaku-tzuki.
Halfstep: Slide right foot to bring alongside left foot whilst guarding with both hands. Ensure knees together and guard is strong (this is a vulnerable position so don't stay there for long!). Then perform Shufflestep as above.
Changeover: Step through with right leg and strike jun tzuki with RH. then perform gyaku tzuki with lh.